The "diagnostic display" mode is entered with the following procedure;

1) Turn on the ignition but don't start the engine.
2) Press the "reset" button to turn off any warning messages
3) Press and hold "options" , press "fuel" four times within a 10-second period.

When first engaged the on-board diagnostics go into an "automatic" mode and cycle through all the modules and their codes automatically.
When the screen displays "manual diagnostics," select the desired module by pressing the "options" button to go forward or the "trip" button to go back. Press "gages" to go forward or "fuel" to go back for each code under a module.

To exit the diagnostic mode at any time, press "E/M". If you want to erase or "clear" codes, press, "reset."

The computer will show two kinds of codes, "current" and "history," designated "C" or "H". A current code indicates a malfunction is present in the system whose module is displaying data. A history code indicates a past problem. You can ignore "U" codes

Here's the modules their and functions;

PCM - Powertrain Control Module .... controls the engine (spark, fuel injectors, etc.) and controls the transmission (automatic). Located in engine compartment below battery and behind passenger side wheel.

TAC - Throttle Actuator Control - It is a seperate computer, but is closely linked to the PCM to assist the PCM in managing the throttle plate position motor and sensors. It receives the signals from the accelerator pedal position sensors. Attached to the PCM

EBCM - Electronic Brake Control Module - controls the BPMV (Brake Pressure Modulation Valve) to provide Anti-Lock Braking, Traction Control, and if equipped, Active Handling. It also controls Magnasteer, and depending on Model Year, may also manage functions such as Dynamic Rear Proportioning. 1999 and later cars it is located in engine compartment, driver's side, just forward of engine and low. 1997 and into 1998 it is located in rear of vehicle close to differential.

ESC - Electronic Suspension Controller - if equipped with F45 (Real Time Damping) or F55 (Magnetic Suspension Ride Control) this computer controls the shock absorbers to provide an adjustable ride. Located in left storage "cubby" in rear of vehicle.

BCM - Body Control Module - This computer manages the vehicle alarm system. It is also responsible for managing vehicle lights (Twilight Sentinal) and based on input from the RFA can unlock doors and turn on "approach lights". Located in passenger footwell to the left of the I/P fuse block.

IPC - Instrument Panel Cluster - Controls the gauge displays, the DIC, and the HUD. Located behind gauge cluster.

HVAC - Heater-Ventilation-Air Conditioning - If equipped, maintains cabin temperature in AUTO mode by selecting appropriate amounts of chilled/heated air based on input from sensors (outside air temp, solar sunload, and cabin temp). Located behind HVAC control panel.

LDCM - Left Door Control Module - manages door lock (under command from BCM or driver), window and mirror. Located inside the left door.
RDCM - Right Door Control Module - same functions as LDCM, located inside the right door.

SCM - Seat Control Module - Main function is for storing and commanding seat and mirror positions in vehicles equipped with Memory option. Attached to underside of passenger seat.

RFA - Remote Function Actuation - Radio receiver/transmitter that works with the key fobs. It also manages the Tire Pressure Monitoring system as it receives the pressure data from the sensors in the wheels. Commands the IPC to display warning messages when a tire is low or flat, for example. Located behind driver, in interior of vehicle, behind upper left trim panel in trunk area.

SDM - Sensing and Diagnostic Module - It controls when the airbags are fired, and constantly runs diagnostic checks to be sure the system is working OK. It contains a capaciter that stores enough electricity to fire the bags even if the battery fails in a crash. It also serves as a "black box" capturing and permanently storing the last 5 seconds of vehicle data prior to the crash. Located inside the center area of the dashboard under the HVAC controller.

10-PCM - Powertrain Control Module
P0101 Mass Air Flow (MAF) System Performance
P0102 Mass Air Flow (MAF) Sensor Circuit Low Frequency
P0103 Mass Air Flow (MAF) Sensor Circuit High Frequency
P0107 Manifold Pressure (MAP) Sensor Circuit Low Voltage
P0108 Manifold Pressure (MAP) Sensor Circuit High Voltage
P0112 Intake Air Temp (IAT) Sensor Circuit Low Voltage
P0113 Intake Air Temp (IAT) Sensor Circuit High Voltage
P0117 Engine Coolant Temp (ECT) Sensor Low Voltage
P0118 Engine Coolant Temp (ECT) Sensor High Voltage
P0118 Engine Coolant Temperature (ECT) Excessive Time to Closed Loop Fuel Control
P0131 Heated Oxygen Sensor (HO2S) Circuit Low Voltage Bank 1 Sensor 1
P0132 Heated Oxygen Sensor (HO2S) Circuit High Voltage Bank 1 Sensor 1
P0133 Heated Oxygen Sensor (HO2S) Slow Response Bank 1 Sensor 1
P0134 Heated Oxygen Sensor (HO2S) Circuit Insufficient Activity Bank 1 Sensor 1
P0135 Heated Oxygen Sensor (HO2S) Heater Circuit Bank 1 Sensor 1
P0137 Heated Oxygen Sensor (HO2S) Circuit Low Voltage Bank 1 Sensor 2
P0138 Heated Oxygen Sensor (HO2S) Circuit High Voltage Bank 1 Sensor 2
P0140 Heated Oxygen Sensor (HO2S) Circuit Insufficient Activity Bank 1 Sensor 2
P0141 Heated Oxygen Sensor (HO2S) Heater Circuit Bank 1 Sensor 2
P0151 Heated Oxygen Sensor (HO2S) Circuit Low Voltage Bank 2 Sensor 1
P0152 Heated Oxygen Sensor (HO2S) Circuit High Voltage Bank 2 Sensor 1
P0153 Heated Oxygen Sensor (HO2S) Slow Response Bank 2 Sensor 1
P0154 Heated Oxygen Sensor (HO2S) Circuit Insufficient Activity Bank 2 Sensor 1
P0155 Heated Oxygen Sensor (HO2S) Heater Circuit Bank 2 Sensor 1
P0157 Heated Oxygen Sensor (HO2S) Circuit Low Voltage Bank 2 Sensor 2
P0158 Heated Oxygen Sensor (HO2S) Circuit High Voltage Bank 2 Sensor 2
P0160 Heated Oxygen Sensor (HO2S) Circuit Insufficient Activity Bank 2 Sensor 2
P0161 Heated Oxygen Sensor (HO2S) Heater Circuit Bank 2 Sensor 2
P0171 Fuel Trim System Lean Bank 1
P0172 Fuel Trim System Rich Bank 1
P0174 Fuel Trim System Lean Bank 2
P0175 Fuel Trim System Rich Bank 2
P0230 Fuel Pump Control Circuit
P0300 Engine Misfire Detected
P0325 Knock Sensor (KS) System
P0327 Knock Sensor (KS) Circuit Front
P0332 Knock Sensor (KS) Circuit Rear
P0335 CKP Sensor Circuit
P0336 CKP Sensor Circuit Performance
P0341 CMP Circuit Performance
P0342 CMP Sensor Circuit Low Voltage
P0343 CMP Sensor Circuit High Voltage
P0351 Ignition Control #1 Circuit
P0352 Ignition Control #2 Circuit
P0353 Ignition Control #3 Circuit
P0354 Ignition Control #4 Circuit
P0355 Ignition Control #5 Circuit
P0356 Ignition Control #6 Circuit
P0357 Ignition Control #7 Circuit
P0358 Ignition Control #8 Circuit
P0410 AIR System
P0412 AIR Solenoid Relay Control Circuit
P0418 AIR Pump Relay Control Circuit
P0420 TWC System Low Efficiency Bank 1
P0430 TWC System Low Efficiency Bank 2
P0441 EVAP System No Flow During Purge
P0461 Fuel Level Sensor 1 Circuit Performance
P0462 Fuel Level Sensor 1 Circuit Low Voltage
P0463 Fuel Level Sensor 1 Circuit High Voltage
P0480 FC Relay 1 Control Circuit
P0481 FC Relay 2 and 3 Control Circuit
P0500 VSS Circuit (M/T)
P0506 Idle Speed Low
P0507 Idle Speed High
P0522 Engine Oil Pressure Sensor Circuit Low Voltage
P0523 Engine Oil Pressure Sensor Circuit High Voltage
P0530 A/C Refrigerant Pressure Sensor Circuit
P0562 System Voltage Low
P0563 System Voltage High
P0567 Cruise Resume Circuit
P0568 Cruise Set Circuit
P0571 Cruise Brake Switch Circuit (M/T)
P0601 PCM Memory
P0602 PCM Not Programmed
P0604 PCM RAM Performance
P0606 PCM Internal Communication Interrupted
P0608 VSS Output Circuit
P0650 MIL Control Circuit
P0654 Engine Speed Output Circuit
P0704 Clutch Switch Circuit (M/T)
P0705 Transmission Range Switch Circuit (A/T)
P0706 Transmission Range Switch Performance (A/T)
P0801 Reverse Inhibit Solenoid Control Circuit (M/T)
P0803 1-4 Upshift Solenoid Control Circuit (M/T)
P0804 1-4 Upshift Lamp Control Circuit (M/T)

P1111 Intake Air Temperature (IAT) Sensor Circuit Intermittent High Voltage
P1112 Intake Air Temperature (IAT) Sensor Circuit Intermittent Low Voltage
P1114 ECT Sensor Circuit Intermittent Low Voltage
P1115 ECT Sensor Circuit Intermittent High Voltage
P1120 TP Sensor 1 Circuit
P1125 APP System
P1133 Heated Oxygen Sensor (HO2S) Insufficient Switching Bank 1 Sensor 1
P1134 Heated Oxygen Sensor (HO2S) Transition Time Ratio Bank 1 Sensor 1
P1153 Heated Oxygen Sensor (HO2S) Insufficient Switching Bank 2 Sensor 1
P1154 Heated Oxygen Sensor (HO2S) Transition Time Ratio Bank 2 Sensor 1
P1220 TP Sensor 2 Circuit
P1221 TP Sensors 1, 2 Performance
P1258 Engine Coolant Over Temperature-Fuel Disabled
P1275 APP Sensor 1 Circuit
P1276 APP Sensor 1 Circuit Performance
P1280 APP Sensor 2 Circuit
P1281 APP Sensor 2 Circuit Performance
P1285 APP Sensor 3 Circuit
P1286 APP Sensor 3 Circuit Performance
P1380 EB (T) CM DTC Detected- Rough Road Data Unusable
P1381 Misfire Detected - No EB (T) CM/PCM Serial Data
P1415 AIR System Bank 1
P1416 AIR System Bank 2
P1431 Fuel Level Sensor 2 Circuit Performance
P1432 Fuel Level Sensor 2 Low Voltage
P1433 Fuel Level Sensor 2 High Voltage
P1441 Evaporative Emissions (EVAP) System Flow During Non-Purge
P1514 TAC System MAF Performance
P1515 Command vs Actual Throttle Position Performance (PCM Module)
P1516 Command vs Actual Throttle Position Performance (TAC Module)
P1517 TAC Module Processor
P1518 PCM to TAC Module Serial Data Circuit
P1539 A/C Clutch Status Circuit High Voltage
P1545 A/C Clutch Relay Control Circuit
P1546 A/C Clutch Status Circuit Low Voltage
P1571 ASR Desired Torque
P1574 Stop Lamp Control Circuit
P1575 Extended Travel Brake Switch Circuit High Voltage
P1626 Theft Deterrent System Fuel Enable Circuit
P1630 Theft Deterrent System PCM In Learn Mode
P1631 Theft Deterrent System Password Incorrect
P1635 5 Volt Reference #1 Circuit
P1639 5 Volt Reference #2 Circuit
P1644 Delivered Torque Output Circuit
P1652 Powertrain Induced Chassis Pitch Output Circuit

28-TCS - Traction Control System
C1214 Sol Valve Relay Contact or Coil CKT Open
C1217 BPMV Pump Motor Relay Contact CKT Open
C1221 LF Wheel Speed Sensor Input Signal is 0
C1222 RF Wheel Speed Sensor Input Signal is 0
C1223 LR Wheel Speed Sensor Input Signal is 0
C1224 RR Wheel Speed Sensor Input Signal is 0
C1225 RF Excessive Wheel Speed Variation
C1226 LF Excessive Wheel Speed Variation
C1227 LR Excessive Wheel Speed Variation
C1228 RR Excessive Wheel Speed Variation
C1232 LF Wheel Speed Circuit Open or Shorted
C1233 RF Wheel Speed Circuit Open or Shorted
C1234 LR Wheel Speed Circuit Open or Shorted
C1235 RR Wheel Speed Circuit Open or Shorted
C1236 Low System Supply Voltage
C1237 High System Supply Voltage
C1241 Magna Steer Circuit Malfunction
C1242 BPMV Pump Motor Ground Circuit Open
C1243 BPMV Pump Motor Stalled
C1255 EBTCM Internal Malfunction
CEBCM Internal Malfunction
C1261 LF Inlet Valve Solenoid Malfunction
C1262 LF Outlet Valve Solenoid Malfunction
C1263 RF Inlet Valve Solenoid Malfunction
C1264 RF Outlet Valve Solenoid Malfunction
C1265 LR Inlet Valve Solenoid Malfunction
C1266 LR Outlet Valve Solenoid Malfunction
C1267 RR Inlet Valve Solenoid Malfunction
C1268 RR Outlet Valve Solenoid Malfunction
C1273 RF TCS Master Cyl Isolation Valve Malfunction
C1274 RF TCS Prime Valve Malfunction
C1276 Delivered Torque Signal CKT Malfunction
C1277 Requested Torque Signal CKT Malfunction
C1278 TCS Temporarily Inhibited By PCM
C1281 Steering Sensor Uncorrelated Malfunction
C1286 Steering Sensor Bias Malfunction
C1287 Steering Sensor Rate Malfunction
C1291 Open Brake Lamp Sw Contacts During Deccel
C1293 DTC C1291/C1292 Set Curnt/Prev Ign Cylce
C1294 Brake Lamp Switch Circuit Always Active
C1295 Brake Lamp Switch Circuit Open
U1016 Loss of Communications with PCM
U1255 Generic Loss Communications
U1300 Class 2 Circuit Shorted to Ground
U1301 Class 2 Circuit Shorted to Battery

38-RTD - Real Time DampingC1650 ESC Module Malfunction
C1658 EEPROM Calibration Malfunction
C1710 LF Shock Absorber Solenoid (Short to Voltage)
C1711 LF Shock Absorber Solenoid (Short to GND)
C1712 LF Shock Absorber Solenoid (Open Circuit)
C1715 RF Shock Absorber Solenoid (Short to Voltage)
C1716 RF Shock Absorber Solenoid (Short to GND)
C1717 RF Shock Absorber Solenoid (Open Circuit)
C1720 LR Shock Absorber Solenoid (Short to Voltage)
C1721 LR Shock Absorber Solenoid (Short to GND)
C1722 LR Shock Absorber Solenoid (Open Circuit)
C1725 RR Shock Absorber Solenoid (Short to Voltage)
C1726 RR Shock Absorber Solenoid (Short to GND)
C1727 RR Shock Absorber Solenoid (Open Circuit)
C1743 Loss of Vehicle Speed Signal
C1760 LF Position Sensor (Out of Range)
C1761 RF Position Sensor (Out of Range)
C1762 LR Position Sensor (Out of Range)
C1763 RR Position Sensor (Out of Range)
C1768 Position Sensor Supply Malfunction (Overcurrent)
C1780 Loss of Steering Position Signal
C1786 RTD Control Relay Malfunction
C1787 RTD Control Relay Circuit (Open or Short to GND)
C1788 RTD Control Relay Circuit (Short to Voltage)
C1790 Ride Control Switch (Out of Range)
C1791 Ride Control Switch (Contact Malfunction)

40-BCM -Body Control Module
B0432 Rear Defogger Relay Circuit
B0433 Rear Defogger Relay Circuit
B0502 RH DRL Relay Circuit
B0503 RH DRL Relay Circuit
B0507 LH DRL Relay Circuit
B0508 LH DRL Relay Circuit
B0605 BCM Internal Memory Function
B0844 BCM Temporarily Inhibit ABS
B2403 Front Fog Lamp Switch Circuit
B2408 Rear Fog Lamp Switch Circuit
B2482 Backup Lamp Relay Circuit
B2483 Backup Lamp Relay Circuit
B2527 Horn Relay Circuit
B2528 Horn Relay Circuit
B2573 Hatch Release Switch Circuit (Short to Voltage)
B2578 RF Turn Signal Monitor Circuit (Short to Voltage)
B2583 LF Turn Signal Monitor Circuit (Short to Voltage)
B2587 Column Lock/Unlock Drive (A)
B2588 Column Lock/Unlock Drive (A)
B2592 Column Lock/Unlock Drive (B)
B2583 Column Lock/Unlock Drive (B)
B2597 Traction Control System Switch Circuit
B2721 PASS-Key Detection Circuit
B2722 PASS-Key Detection Circuit
B2723 PASS-Key Detection Circuit
B2735 PASS-Key Programming Mode Active
U1016 Loss of Communications with PCM
U1096 Loss of Communications with IPC
U1255 Serial Data Line Malfunction

60-IPC - Instrument Panel ClusterB0516 Speedometer Signal Circuit Malfunction
B0521 Tachometer Signal Circuit Malfunction
B1512 DIC Switch 1 Signal Short to GND "FUEL"
B1517 DIC Switch 2 Signal Short to GND "GAGES"
B1522 DIC Switch 3 Signal Short to GND "TRIP"
B1527 DIC Switch 4 Signal Short to GND "OPTIONS"
B1532 DIC Switch 5 Signal Short to GND "E/M"
B1537 DIC Switch 6 Signal Short to GND "RESET"
B1542 Oil Temperature Circuit Short to GND
B1543 Oil Temperature Circuit Open
U1016 Loss of Communications with PCM
U1040 Loss of Communications with TCS
U1056 Loss of Communications with RTD
U1064 Loss of Communications with BCM
U1128 Loss of Communications with Radio
U1153 Loss of Communications with HVAC
U1160 Loss of Communications with LDCM
U1161 Loss of Communications with RDCM
U1166 Loss of Communications with SCM
U1176 Loss of Communications with RFA
U1255 Serial Data Line Malfunction

99-HVAC - Heater, Ventilation, Air Conditioning
B0332 Outside Air Temp Sensor Short to GND
B0333 Outside Air Temp Sensor Open
B0337 Inside Air Temp Sensor Short to GND
B0338 Inside Air Temp Sensor Open
B0348 Sunload Temperature Sensor Open
B0361 Left Actuator Feedback Short to GND
B0363 Left Actuator Feedback Open
B0365 Right Actuator Feedback Short to GND
B0367 Right Actuator Feedback Open
B0441 Left Actuator Out of Range
B0446 Right Actuator Out of Range
B1016 Loss of Communications with PCM
U1064 Loss of Communications with BCM
U1096 Loss of Communications with IPC
U1255 Serial Data Line Malfunction

A0-LDCM - Left Door Control Module
B2202 Left Window Up Switch Fault
B2204 Left Window Down Switch Fault
B2206 Right Window Up Switch Fault
B2208 Right Window Down Switch Fault
B2222 LT Mirror Select Switch Fault
B2224 RT Mirror Select Switch Fault
B2226 Mirror Right Switch Fault
B2228 Mirror Left Switch Fault
B2232 Mirror Up Switch Fault
B2234 Mirror Down Switch Fault
B2236 Left Door Lock Switch Fault
B2238 Left Door UnLock Switch Fault
B2242 Memory 1 Switch Fault
B2244 Memory 2 Switch Fault
B2252 Key Cylinder Switch Fault
B2262 Horizontal Position Sensor Fit
B2264 Vertical Position Sensor Fault
B2272 Left Mirror Motor Fault
B2274 Window Motor Fault
B2276 Door Lock Motor/Mirror Heater Fit
B2282 Battery #1 Fault
B2284 Battery #2 Fault
B2286 +5V Reference Fault
U1064 Loss of Communications with BCM
U1096 Loss of Communications with IPC
U1255 Serial Data Line Malfunction

A1-RDCM - Right Door Control Module
B2203 Right Window Up Switch Fault
B2205 Right Window Down Switch Fault
B2237 Right Door Lock Switch Fault
B2239 Right Door Un-Lock Switch Fault
B2253 Key Cylinder Switch Fault
B2263 Horizontal Position Sensor Fit
B2265 Horizontal Position Sensor Fault
B2273 Right Mirror Motor Fault
B2275 Window Motor Fault
B2277 Door Lock Motor/Mirror Heater Fit
B2283 Battery #1 Fault
B2285 Battery #2 Fault
B2287 +5V Reference Fault
U1064 Loss of Communications with BCM
U1096 Loss of Communications with IPC
U1255 Serial Data Line Malfunction

A6-SCM - Seat Control Module
B0846 Battery 2 Out of Range
B0851 Battery 1 Out of Range
B2002 Fore/Aft Seat Motor Open or Short to GND
B2007 Front Vertical Seat Motor Open or Shorted
B2012 Rear Vertical Seat Motor Open or Shorted
B2172 Seat Front Up Switch Shorted to GND
B2177 Seat Front Down Switch Shorted to GND
B2182 Seat Rear Up Switch Shorted to GND
B2187 Seat Rear Down Switch Shorted to GND
B2192 Seat Forward Switch Shorted to GND
B2197 Seat Reverse Switch Shorted to GND
B2605 Seat Front Vertical Position Sensor Failure
B2606 Seat Rear Vertical Position Sensor Failure
B2607 Seat Horizontal Position Sensor Failure

B0-RFA - Remote Function Actuation
B0605 Receiver Internal Memory Malfunction
B2805 No Transmitters Programmed
C2100 Left Front TPM Sensor Malfunction
C2105 Right Front TPM Sensor Malfunction
C2110 Right Rear TPM Sensor Malfunction
C2115 Left Rear TPM Sensor Malfunction
C2120 TPM System Malfunction (No Sensors Received)
C2121 TPM System Programming Malfunction (No Sensors Programmed)
U1000 Loss of Communication Undetermined
U1016 Loss of Communication with PCM
U1064 Loss of Communication with BCM
U1096 Loss of Communication with IPC
U1255 Serial Data Line Malfunction

Hey does everybody see the SDM with no codes. I never see the sdm come up on my display. I see the others fine.

sounds like a pain in butt to me??

Hey tstar,
I'm a 1st time vette owner and 1st time post to this site. Your info is awesome. My 2001-C5 has check engine light on. Ran diagnostics and got a P0440 and P0443 under PCM. Codes are not on your listing. Can you steer me in right direction with this? Tank

Hey Tank,

Are they H or C? Looks like your EVAP system is acting up on you. I hope this pastes good in here for you;

DTC P0440
Description

The EVAP large leak test applies vacuum to the evaporative emission (EVAP) system and monitors vacuum decay. The control module monitors the fuel tank pressure (FTP) sensor signal to determine the vacuum decay rate. At an appropriate time, the control module turns the EVAP canister purge valve ON (open) and the EVAP vent valve ON (closed). This allows the engine to draw a vacuum on the EVAP system. At a calibrated time, or vacuum level, the control module turns the purge valve OFF (closed), sealing the system, and monitors the FTP sensor input in order to determine EVAP system vacuum. If the system is unable to achieve the calibrated vacuum level, or the vacuum level decreases too rapidly, DTC P0440 will set.

Conditions for Running the DTC
DTC P0107. P0108, P0112, P0113, P0117, P0118, P0125, P0443, P0449, P0452, P0453, P1106. P1107, P1112, P1114, P1115, P1120, P1220 or P1221 are not set.
The ignition voltage is between 10 and 18 volts.
The barometric pressure is more than 75 kPa.
The fuel level is between 15 and 85 percent.
The engine coolant temperature (ECT) is between 4°C and 30°C (39°F and 86°F).
The intake air temperature (IAT) is between 4°C and 30°C (39°F and 86°F).
The start up ECT and IAT are within 9°C (16°F) of each other.
The vehicle speed sensor (VSS) is less than 121 km/hr (75mph).

Conditions For Setting the DTC
The EVAP system is not able to achieve or maintain vacuum during the diagnostic test.
Action Taken When the DTC Sets
The control module will illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test ran and failed.
The control module will store conditions which were present when the DTC set as Freeze Frame and Failure Records data.

Conditions for Clearing the MIL/DTC
The control module will turn the malfunction indicator lamp (MIL) OFF during the first trip in which the diagnostic has been run and passed.
A last test failed (current DTC) clears when the control module turns OFF the MIL.
The history DTC will clear after the control module runs and passes 40 consecutive warm up cycles with no failure.
The DTC can be cleared by using a scan tool.

Diagnostic Aids
Use the EVAP pressure/purge diagnostic station in order to pressurize the EVAP system to aid in locating intermittent leaks. Move all EVAP components while testing with the Ultrasonic Leak Detector.
A temporary blockage in the EVAP canister purge valve, purge pipe or EVAP canister could cause an intermittent condition. To repair a blockage in the EVAP system refer to
Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

DTC P0443
Circuit Description

An ignition voltage is supplied directly to the evaporative emission (EVAP) purge valve. The EVAP purge valve is pulse width modulated (PWM). The control module controls the EVAP purge valve ON time by grounding the control circuit via an internal switch called a driver. The scan tool displays the amount of ON time as a percentage. The control module monitors the status of the driver. If the control module detects an incorrect voltage for the commanded state of the driver, DTC P0443 sets.

Conditions for Running the DTC
The engine speed is more than 400 RPM.
The system voltage is between 6-18 volts.

Conditions for Setting the DTC
The control module detects that the commanded state of the driver and the actual state of the control circuit do not match.
The above conditions are present for a minimum of 5 seconds.

Action Taken When the DTC Sets
The control module will illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test ran and failed.
The control module will store conditions which were present when the DTC set as Freeze Frame and Failure Records data.

Conditions for Clearing the MIL/DTC
The control module will turn OFF the MIL during the third consecutive trip in which the diagnostic ran and passed.
The History DTC will clear after 40 consecutive warm-up cycles without a malfunction.
The DTC can be cleared with a scan tool.

Thanks for the quick reply and info tstar. Have H and C both. I cleared codes and will see how soon they come back. Got a state inspection coming up this month and need to get it right to pass emission test. Is EVAP related to fuel tank pressure? tank

Yes, it's related. The EVAP system is designed to not allow gas fumes to escape. It's possible you didn't tighten your gar cap tight enough after the last fill up also... Hopefully they won't come back.

Now you might need to have a dealer with a Tech II clear the codes from history (unless you think you'll start the car 40 times prior to your inspection) as some states will fail you if there codes stored related to emissions...

Tim

I checked gas cap 1st thing when wife told me about light on. Looked ok. Does history not clear when I cleared codes with on-board system? When I re-ran diagnostics it showed no codes. I have a friend with a snap-on scanner tool that I could get to clear codes further if needed.
Man.... wife and I are excited about this car. It has 18k original miles and never been in the rain. Not a scratch and still smells like new. Bought it from original owner that had to sell it cause he lost his job. Thinking about some small mods like k&n intake system and corsa exhaust. Are there any worth-while chips available for a stock LS1/350hp? Appreciate your help, tank.

Conditions for Clearing the MIL/DTC
The control module will turn the malfunction indicator lamp (MIL) OFF during the first trip in which the diagnostic has been run and passed.
A last test failed (current DTC) clears when the control module turns OFF the MIL.
The history DTC will clear after the control module runs and passes 40 consecutive warm up cycles with no failure.
The DTC can be cleared by using a scan tool.

They'll stay in history for 40 cold starts. I don't think a regular scan tool will do it, only a Tech II that the dealer has.

Personally I don't like the K&N stuff for the C5, there are better options. I like the Hurricane and Calloway, alot of owners swear by Varram... If you do a search in C5 Forum you should get a ton of results. I have the Corsa Indies and like em, pricey though...

Nope no easy chip swapping in these, you have to have your PCM reprogrammed. IF you have an auto and do not plan any other Mods then what you listed, a handheld is a good option.

Tim

Found 2 wires, near the EVAP test port underneath left fuel rail cover, chewed into by furry creature. Also found lining chewed off of the hood liner on the left side. Repaired wires and cleared codes. Car still has a strong gasoline odor surrounding it, especially when you drive it, but does not show any leaks on the ground. Suspect that rat chewed a vapor hose somewhere. Do you know of any common areas that rats like to hide and chew on the C5s?
Ron

If you clear a c code will it come back if it still has the problem i was trying to clear an h code and ended up clearing the wrong code. Just learning how to work this thing

TStar

Thanks for the info.

Excellent info.

So if i do this will the codes be able to tell me what is wrong with my memory seats or if it is the SCM as i suspect ?

Thnks for the great info.