Engine Control System Diagnosis - 4.3l (DTC p0140 to p2610) Chevrolet Chevy Express G2500

Circuit Description

Heated oxygen sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature. The powertrain control module (PCM) supplies the HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started the PCM operates in open loop, ignoring the HO2S voltage signal. Once the HO2S reaches operating temperature and closed loop is achieved, the HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage. High HO2S voltage indicates a rich exhaust stream; low HO2S voltage indicates a lean exhaust stream. This diagnostic will only run once per ignition cycle. If the PCM detects that the HO2S voltage remains within the bias voltage range, DTC P0140 sets for HO2S bank 1 sensor 2 or DTC P0160 sets for HO2S bank 2 sensor 2

Conditions for Running the DTC

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0141, P0161, P0200, P0300, P0442, P0446, P0452, P0453, P0455, P0496 are not set.
2. The Engine Run Time parameter is more than 300 seconds.
3. The Loop Status is closed.
4. The Ignition 1 Signal parameter is between 10-18 volts.

Conditions for Setting the DTC

1. The PCM detects that the affected HO2S voltage parameter is between 410-490 mV for 150 seconds.
2. The TP Sensor parameter changes more than 5 percent within 1 second, 6 times.

Action Taken When the DTC Sets

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

Test Description

The number below refers to the step number on the diagnostic table.

1. 2: If the voltage is varying above and below the specified value, the condition is not present.

DTC P0140 or P0160

The powertrain control module (PCM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy and emission control. Fuel delivery is controlled differently during Open and Closed Loop. During Open Loop the PCM determines fuel delivery based on sensor signals without oxygen sensor input. During Closed Loop the PCM adds oxygen sensor inputs and level of purge to calculate Short and Long Term fuel trim adjustments. If the oxygen sensors indicate a lean condition, fuel trim values will be above 0 percent. If the oxygen sensors indicate a rich condition, fuel trim values will be below 0 percent. The values for the Short Term fuel trim change rapidly in response to the heated oxygen sensor (HO2S) voltage signals. Long Term fuel trim makes coarse adjustments in order to maintain an Air/Fuel Ratio of 14.7:1. A block of cells contain information arranged in combinations of engine RPM and engine load for a full range of vehicle operating conditions. The long term fuel trim diagnostic is based on an average of cells currently being used. The PCM selects the cells based on the engine speed and engine load. If the PCM detects an excessively lean condition, DTC P0171 or P0174 sets.

1. DTCs P0101, P0103, P0108, P0135, P0137, P0141, P0200, P0300, P0410, P0420, P0430, P0440, P0442, P0443, P0446, P0449, P0506, P0507 or P1441 are not set.
2. The engine coolant temperature (ECT) is between 75-115°C (167-239°F).
3. The intake air temperature (IAT) is between -20 to +90°C (+4 and +194°F).
4. The manifold absolute pressure (MAP) is between 26-90 kPa (3.7-13 psi).
5. The vehicle speed is less than 137 km/h (85 mph).
6. The engine speed is between 400-3,000 RPM.
7. The barometric pressure (BARO) is more than 74 kPa (10.7 psi).
8. The mass airflow (MAF) is between 5-90 g/s.
9. The fuel level is more than 10 percent.
10. The throttle position (TP) is less than 90 percent.

1. The average long term fuel trim cell value is above 23 percent.
2. All of the above conditions are present for 6 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

Diagnostic Aids

1. The system will go lean if an injector is not suppling enough fuel.
2. A lean condition could be present during high fuel demand.
3. Use a scan tool in order to review the Failure Records. If an intermittent condition is suspected, refer to «Intermittent Conditions»(/chevrolet/chevy-express-g2500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-troubleshooting__intermittent-conditions) .

The numbers below refer to the step numbers on the diagnostic table.

1. 5: If conditions were not corrected, refer to Fuel System Diagnosis for a possible fuel problem.
2. 6: If conditions were not corrected, a worn cam, worn intake or exhaust valves, or other engine mechanical failure may be the problem.

DTC P0171 or P0174

The powertrain control module (PCM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy and emission control. Fuel delivery is controlled differently during Open and Closed Loop. During Open Loop the PCM determines fuel delivery based on sensor signals, without oxygen sensor input. During Closed Loop the PCM adds oxygen sensor inputs and level of purge to calculate Short and Long Term fuel trim adjustments. If the oxygen sensors indicate a lean condition, fuel trim values will be above 0 percent. If the oxygen sensors indicate a rich condition, fuel trim values will be below 0 percent. The values for the Short Term fuel trim change rapidly in response to the heated oxygen sensor (HO2S) voltage signals. Long Term fuel trim makes coarse adjustments in order to maintain an Air/Fuel Ratio of 14.7:1. A block of cells contain information arranged in combinations of engine RPM and engine load for a full range of vehicle operating conditions. The long term fuel trim diagnostic is based on an average of cells currently being used. The PCM selects the cells based on the engine speed and engine load. The fuel trim diagnostic will conduct a test to determine if a rich failure actually exists or if excessive vapor from the evaporative emission (EVAP) canister is causing a rich condition. If the PCM detects an excessively rich condition, DTC P0172 or P0175 sets.

1. DTCs P0101, P0103, P0108, P0135, P0137, P0141, P0200, P0300, P0410, P0420, P0430, P0440, P0442, P0443, P0446, P0449, P0506, P0507 or P1441 are not set.
2. The engine coolant temperature (ECT) is between 75-115°C (167-239°F).
3. The intake air temperature (IAT) is between -20 to +90°C (4-194°F).
4. The manifold absolute pressure (MAP) is between 26-90 kPa (3.7-13 psi).
5. The vehicle speed is less than 137 km/h (85 mph).
6. The engine speed is between 400-3,000 RPM.
7. The barometric pressure (BARO) is more than 74 kPa (10.7 psi).
8. The mass airflow (MAF) is between 5-90 g/s.
9. The fuel level is more than 10 percent.
10. The throttle position (TP) is less than 90 percent.

1. The average long term fuel trim value is below -13 percent.
2. All of the above conditions are present for 40 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. Fuel contamination, such as water or alcohol will effect fuel trim.
2. A malfunctioning mass air flow sensor can cause a rich condition and set this DTC. Refer to «DTC P0101»(/chevrolet/chevy-express-g2500/1996-2012/remont/testing-diagnostics/#engine-control-system-diagnosis-43l-dtc-p0016-to-p0138-or-p0158) .
3. Use a scan tool in order to review Failure Records. If an intermittent condition is suspected, refer to «Intermittent Conditions»(/chevrolet/chevy-express-g2500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-troubleshooting__intermittent-conditions) .

The numbers below refer to the step numbers on the diagnostic table.

1. 5: If conditions were not corrected, refer to Fuel System Diagnosis for a possible fuel problem.
2. 6: An EVAP canister that is saturated will cause a rich condition. If the conditions were not corrected, a worn cam, worn intake or exhaust valves, or other engine mechanical failure may be the problem.

DTC P0172 or P0175

The control module enables the appropriate fuel injector pulse for each cylinder. Ignition voltage is supplied to the fuel injectors. The control module controls each fuel injector by grounding the control circuit via a solid state device called a driver. The control module monitors the status of each driver. If the control module detects an incorrect voltage for the commanded state of the driver, a fuel injector control DTC sets.

1. The engine is running.
2. The ignition voltage is between 6-18 volts.

1. The control module detects an incorrect voltage on the fuel injector control circuit.
2. The above condition is met for 5 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. Performing the Fuel Injector Coil Test may help isolate an intermittent condition. Refer to «Fuel Injector Coil Test»(/chevrolet/chevy-express-g2500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-troubleshooting) .
2. For an intermittent condition, refer to «Intermittent Conditions»(/chevrolet/chevy-express-g2500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-troubleshooting__intermittent-conditions) .

DTC P0200

The control module enables the fuel pump relay when the ignition switch is turned ON. The control module will disable the fuel pump relay within two seconds unless the control module detects ignition reference pulses. The control module continues to enable the fuel pump relay as long as ignition reference pulses are detected. The control module disables the fuel pump relay within 2 seconds if ignition reference pulses cease to be detected and the ignition remains ON.

The control module monitors the voltage on the fuel pump relay control circuit. If the control module detects an incorrect voltage on the fuel pump relay control circuit, a fuel pump relay control DTC sets.

1. The engine speed is more than 400 RPM.
2. The ignition voltage is between 6-18 volts.

1. The control module detects that the commanded state of the driver and the actual state of the control circuit do not match.
2. The above condition is met for a minimum of 2.5 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

DTC P0230

System Description

The powertrain control module (PCM) uses information from the crankshaft position (CKP) sensor and the camshaft position (CMP) sensor in order to determine when an engine misfire is occurring. By monitoring variations in the crankshaft rotation speed for each cylinder, the PCM is able to detect individual misfire events. A misfire rate that is high enough can cause the 3-way catalytic converter (TWC) to overheat under certain driving conditions. The malfunction indicator lamp (MIL) will flash ON and OFF when the conditions for TWC overheating are present. If the PCM detects a misfire rate sufficient to cause emission levels to exceed mandated standards, DTC P0300 will set.

1. DTC P0016, P0101, P0102, P0103, P0106, P0107, P0108, P0116, P0117, P0118, P0125, P0128, P0315, P0335, P0336, P0341, P0502, P0503, P1114, P1115, P1121, are not set.
2. The engine speed is between 450-5,000 RPM.
3. The ignition voltage is between 10-18 volts.
4. The engine coolant temperature (ECT) is between -7 and +130°C (19-266°F).
5. The fuel level is more than 10 percent.
6. The throttle angle is steady within 1 percent.
7. The anti-lock brake system (ABS) and the traction control system are not active.
8. The transmission is not changing gears.
9. The A/C clutch is not changing states.
10. The PCM is not in fuel shut-off or decel fuel cut-off mode.
11. The PCM is not receiving a rough road signal.

The PCM is detecting a crankshaft rotation speed variation indicating a misfire sufficient to cause emission levels to exceed mandated standards.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. Excessive vibration from sources other than the engine could cause DTC P0300 to set. The following are possible sources of vibration: Variable thickness brake rotors-Refer to «Symptoms - Hydraulic Brakes»(/chevrolet/chevy-express-g2500/1996-2012/remont/mechanical-hydraulic/#hydraulic-brake-system__symptoms-hydraulic-brakes) in Hydraulic Brakes. Drive shaft not balanced-Refer to «Vibration Analysis - Driveline»(/chevrolet/chevy-express-g2500/1996-2012/remont/oem-general-information/#vibration-symptoms-diagnosis-and-correction) in Vibration Diagnosis and Correction. Worn or damaged accessory drive belt-Refer to «Symptoms - Engine Mechanical»(/chevrolet/chevy-express-g2500/1996-2012/remont/mechanical/#engine-mechanical-43l) in Engine Mechanical.
2. There may be more or less cylinders actually misfiring than indicated by the scan tool.
3. Spray water on the secondary ignition components using a spray bottle. Look and listen for arcing or misfiring.

The number below refers to the step number on the diagnostic table.

1. 2: If the actual CKP variation values are not within the learned values, the misfire counters may increment.

DTC P0300

The crankshaft position (CKP) system variation learn feature is used to calculate reference period errors caused by slight tolerance variations in the crankshaft and the CKP sensor. The calculated error allows the powertrain control module (PCM) to accurately compensate for reference period variations. This enhances the ability of the PCM to detect misfire events over a wider range of engine speed and load conditions.

The PCM stores the CKP system variation values after a learn procedure has been performed. If the actual crankshaft position variation is not within the crankshaft position system variation compensating values stored in the PCM, DTC P0300 may set. If the PCM detects the CKP system variation values are not stored in the PCM memory, DTC P0315 sets.

1. DTCs P0335, P0336, P0341, P1345 are not set.
2. The engine coolant temperature (ECT) is more than 65°C (149°F).

The CKP system variation values are not stored in the PCM memory.

1. The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

DTC P0315

The knock sensor (KS) produces an AC voltage at all engine speeds and loads. The powertrain control module (PCM) then adjusts the spark timing based on the amplitude and frequency of the KS signal. The PCM uses the KS signal to calculate the average voltage. Then the PCM assigns a voltage value. The PCM checks the KS and related wiring by comparing the actual knock signal to the assigned voltage range. A normal KS signal should stay within the assigned voltage range. This diagnostic trouble code (DTC) will set if the PCM malfunctions in a manner that will not allow proper diagnosis of the KS system.

The engine run time is more than 10 seconds.

The PCM detects a malfunction in the KS diagnostic circuitry that will not allow proper diagnosis of the KS system.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. The knock sensor must be torqued correctly to 25 N.m (18 lb ft).
2. The mounting between the sensor and engine must be free of burrs, casting flash, and foreign material.
3. The knock sensor (KS) head is clear from hoses, brackets, and engine electrical wiring.

DTC P0325

The powertrain control module (PCM) monitors a knock sensor (KS) in order to determine if detonation is present. The KS produces an AC voltage at all engine speeds and loads. The powertrain control module (PCM) then adjusts the spark timing based on the amplitude and frequency of the KS signal. The PCM uses the KS signal to calculate the average voltage and then assigns a voltage range value. The PCM should monitor the KS signal within the assigned voltage range. This diagnostic trouble code (DTC) will set if the KS signal is outside the assigned voltage range or the KS signal is not present.

1. DTCs P0117, P0118, P0122, P0123, or P0125 are not set.
2. The engine speed is between 2,000-3,000 RPM.
3. The engine run time is more than 10 seconds.
4. The engine coolant temperature (ECT) is more than 60°C (140°F).
5. The manifold absolute pressure (MAP) is less than 44 kPa.
6. The system voltage is more than 10 volts.

The PCM detects that the KS signal is outside the assigned voltage range or the KS signal is not present.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. Inspect the KS for physical damage. A KS that is dropped or damaged may cause a DTC to set.
2. Inspect the KS for proper installation. A KS that is loose or over torqued may cause a DTC to set. The KS mounting surface must be free of burrs, casting flash, and foreign material.
3. The KS should be clear of hoses, brackets, and engine electrical wiring.
4. For an intermittent condition, refer to «Intermittent Conditions»(/chevrolet/chevy-express-g2500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-troubleshooting__intermittent-conditions) .

The numbers below refer to the step numbers on the diagnostic table.

1. 2: This step ensures the malfunction is present.
2. 3: This step tests the KS for proper operation.
3. 6: If the KS signal wire is shorted to ground or is shorted to voltage, the KS may still produce a signal.
4. 7: If the KS low reference is shorted to ground or is shorted to voltage, the KS may still produce a signal.

DTC P0327

The powertrain control module (PCM) uses the crankshaft position (CKP) sensor to detect crankshaft speed and position. The CKP sensor connects to the PCM through the following circuits

1. The 12-volt reference circuit
2. The low reference circuit
3. The CKP sensor 1 signal circuit

If the PCM detects no signal from the CKP sensor for more than 3 seconds, DTC P0335 sets.

1. DTCs P0101, P0102, P0103, P0341 are not set.
2. The camshaft position (CMP) sensor is incrementing.
3. The mass air flow (MAF) is more than 3 g/s while the engine is cranking.
4. The MAF is more than 5 g/s while the engine is running.

The PCM detects no signal from the CKP sensor for more than 3 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

DTC P0335

The powertrain control module (PCM) uses the crankshaft position (CKP) sensor to detect crankshaft speed and position. The CKP sensor connects to the PCM through the following circuits

1. The 12-volt reference circuit
2. The low reference circuit
3. The CKP sensor 1 signal circuit

If the PCM detects that the CKP sensor signal is incorrect for 3 seconds, DTC P0336 sets.

The engine is cranking or running.

The PCM detects that the CKP sensor signal is incorrect for 3 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers on the diagnostic table.

1. 2: This step verifies that the malfunction is present.
2. 3: This step tests for electromagnetic interference (EMI) on the CKP sensor circuits.

DTC P0336

The camshaft position (CMP) sensor is a hall-effect type sensor. The sensor produces one signal for each revolution of the camshaft in order to control the sequential fuel injection. The CMP sensor is designed to detect changes in a magnetic field. The powertrain control module (PCM) supplies the CMP sensor with the following circuits

1. A 12-volt reference circuit
2. A low reference circuit
3. A signal circuit

The CMP sensor produces a magnetic field whenever the ignition is ON. The CMP sensor is mounted near a reluctor wheel that is attached to the distributor shaft. When the distributor shaft rotates, and the reluctor wheel tooth passes by the CMP sensor, there is a change in the magnetic field. The CMP sensor converts each change in the magnetic field into a PULSE. If the PCM does not detect the CMP signal while the engine is running, diagnostic trouble code (DTC) P0341 will set.

The engine is running.

The CMP sensor reference pulse is not detected once every 2 crankshaft revolutions.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. If the condition is intermittent, refer to «Intermittent Conditions»(/chevrolet/chevy-express-g2500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-troubleshooting__intermittent-conditions) .
2. Electromagnetic interference (EMI) from the ignition coil or from the spark plug wires could cause a faulty signal condition in the CMP signal circuit to the PCM. Ensure that the routing of the CMP circuitry is correct.

The number below refers to the step number on the diagnostic table.

1. 6: This step tests the CMP sensor signal circuit. Applying a voltage causes the CMP sensor high to low and low to high parameter to increase if the circuit and the PCM are operating properly.

DTC P0341

The enhanced ignition system uses the crankshaft position (CKP) sensor to provide a timing input to the control module. Ignition control (IC) spark timing for each cylinder is based on this input. The control module provides the ignition timing signal to the ignition control module (ICM) to control the ignition coil. Each timing pulse detected by the ICM allows the ICM to energize the ignition coil. A large secondary ignition voltage is induced in the secondary coil winding by the primary coil winding. This high voltage is switched to the correct spark plug by the distributor. If the powertrain control module (PCM) detects an unusually high or low voltage on the ignition signal circuit, DTC P0351 sets.

The engine is cranking.

The ignition control voltage is not between 0.04-4.9 volts.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers on the diagnostic table.

1. 2: This step determines if the DTC is an intermittent.
2. 3: This step checks if the IC timing signal from the PCM is available at the ignition control module.

DTC P0351

The three-way catalytic converter (TWC) reduces emissions of hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx). The catalyst within the converter promotes a chemical reaction, which oxidizes the HC and CO that are present in the exhaust gas. This process converts these chemicals into water vapor and Carbon Dioxide (CO2), and will reduce the NOx by, converting them into nitrogen. The catalytic converter also stores oxygen. The powertrain control module (PCM) monitors this process using heated oxygen sensor (HO2S) bank 1 sensor 2 and HO2S bank 2 sensor 2, located in the exhaust stream after the TWC. These sensors are referred to as the catalyst monitor sensors. The catalyst monitor sensors produce an output signal the PCM uses to indicate the oxygen storage capacity of the catalyst. This determines the catalyst's ability to effectively convert the exhaust emissions.

If the catalyst is functioning correctly, the HO2S bank 1 sensor 2 and HO2S bank 2 sensor 2 signals will be far less active than the signals that are produced by HO2S bank 1 sensor 1 and HO2S bank 2 sensor 1. This indicates that the TWC oxygen storage capacity is at an acceptable threshold. When the response time of the catalyst monitor sensors are close to that of the fuel control sensors, the ability of the catalyst to store oxygen may be below an acceptable threshold.

The PCM performs this diagnostic test at idle. When the Conditions for Running this DTC are met, the following occurs

1. The air-to-fuel ratio transitions from lean to rich.
2. The air-to-fuel ratio transitions a second time rich to lean, opposite the first air-to-fuel ratio transition.
3. The PCM captures the response time of the front and the rear HO2S when the air-to-fuel ratio transitions occur. The HO2S response time changes from less than 350 mV to more than 600 mV, and from more than 600 mV to less than 350 mV.
4. The PCM measures the time necessary for the rear HO2S voltage to cross a reference lean-to-rich threshold, and the time necessary for the front HO2S voltage to cross the same lean-to-rich threshold. The difference between the front HO2S time and the rear HO2S time indicates the oxygen storage capacity of the catalyst. If the PCM detects that this time difference is less than a predetermined value, DTC P0420 for bank 1 or P0430 for bank 2 sets.

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0151, P0152, P0153, P0154, P0155, P0171, P0172, P0174, P0175, P0200, P0300, P0325, P0327, P0335, P0336, P0341, P0442, P0443, P0446, P0452, P0453, P0455, P0502, P0503, P0506, P0507, P1133, P1134, P1153 are not set.
2. The intake air temperature (IAT) is between -7 and +85°C (20-185°F).
3. The barometric pressure (BARO) is more than 74 kPa (10.7 psi).
4. The engine coolant temperature (ECT) is between 70-120°C (158-248°F).
5. Since the end of the last idle period, the engine speed has been more than 900 RPM for 46 seconds.
6. The Closed Loop fuel control is enabled.
7. The engine must be at a stable idle speed within 200 RPM of desired idle.

The PCM determines that the oxygen storage capability of the TWC has degraded to less than a calibrated threshold.

1. The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. The catalyst test may abort due to a change in the engine load. Do not change the engine load, ensure the AC is OFF and the engine cooling fans are not cycling, while a catalyst test is in progress.
2. These conditions may cause a catalytic converter to degrade. Inspect for the following conditions: An engine misfire High engine oil or high coolant consumption Retarded spark timing A weak or poor spark A lean fuel mixture A rich fuel mixture A damaged oxygen sensor or wiring harness
3. If the condition is determined to be intermittent, refer to «Intermittent Conditions»(/chevrolet/chevy-express-g2500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-troubleshooting__intermittent-conditions) .
4. If an intermittent condition cannot be duplicated, the information included in Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC was set.
5. The catalyst may have been temporarily contaminated with a chemical from a fuel additive, fuel contamination or any of the above conditions.

The numbers below refer to the step numbers on the diagnostic table.

1. 5: This step indicates that a catalytic converter which has been discolored may be due to an engine running rich, lean or had a previous sever misfire. Verifying the fuel trim percentages may be of assistance in determining if such a condition exists.
2. 6: This step inspects for conditions that can cause the three-way catalytic converter efficiency to appear degraded.

DTC P0420 or P0430

This diagnostic tests the evaporative emission (EVAP) system for a small leak when the ignition is turned OFF, and the correct conditions are met.

Heat from the exhaust system is transferred into a vehicle fuel tank while the vehicle is operating. When the ignition is turned OFF, a change in the fuel tank vapor temperature occurs. With the EVAP system sealed, this results in corresponding pressure changes in the fuel tank vapor space. This change is monitored by the control module using the fuel tank pressure sensor input. The control module then makes a judgement on the integrity of the system. With a 0.51 mm (0.020 inches) leak in the system, the amount of pressure change observed is significantly less than that of a sealed system.

If the control module detects a pressure change less than a calibrated amount, DTC P0442 sets.

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0125, P0335, P0336, P0341, P0351, P0443, P0446, P0449, P0452, P0453, P0455, P0496, P0500, P0502, P0503, P1106, P1107, P1683 are not set.
2. The diagnostic runs once with a 10 hour minimum between tests after a fail.
3. DTC P0455 must run and pass.
4. The start up intake air temperature (IAT) is between 4-30°C (39-86°F).
5. The start up engine coolant temperature (ECT) is less than 30°C (86°F).
6. The start up IAT and ECT are within 8°C (15°F).
7. The barometric pressure (BARO) is more than 74 kPa.
8. The ambient air temperature is between 2-32°C (36-90°F).
9. The engine run time minimum is 10 minutes.
10. The odometer displays more than 10 miles.
11. The vehicle has traveled more than 3 miles this trip.
12. The ECT is more than 70°C (158°F).
13. The fuel level is between 15-85 percent.
14. The ignition is OFF.

The control module detects a pressure change that is less than a calibrated amount.

1. The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. To help locate intermittent leaks, use the J 41413-200 Evaporative Emissions System Tester (EEST) to introduce smoke into the EVAP system. Move all EVAP components while observing smoke with the J 41413-SPT High Intensity White Light.
2. To improve the visibility of the smoke exiting the EVAP system, observe the suspected leak area from different angles with the J 41413-SPT .
3. A condition may exist where a leak in the EVAP system only exists under a vacuum condition. By using the scan tool Purge/Seal function to create a vacuum, seal the system and observe the FTP parameter for vacuum decay, this type of leak may be detected.
4. For intermittent conditions, refer to «Intermittent Conditions»(/chevrolet/chevy-express-g2500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-troubleshooting__intermittent-conditions) .

The numbers below refer to the step numbers on the diagnostic table.

1. 3: Introducing smoke in 15 second intervals may allow smaller leak areas to be more noticeable. When the system is less pressurized, the smoke will sometimes escape in a more condensed manner.
2. 5: This step verifies that repairs are complete and that no other condition is present.

DTC P0442

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

1. The engine speed is more than 400 RPM.
2. The system voltage is between 6-18 volts.

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

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers on the diagnostic table.

1. 2: This step tests if the concern is active. The evaporative emission (EVAP) canister purge solenoid valve is pulse width module (PWM). You should hear a clicking sound when the EVAP canister purge solenoid valve is commanded to 50 percent. The clicking sound should stop when the EVAP canister purge solenoid valve is commanded to 0 percent. The rate at which the valve cycles should increase when the commanded state is increased, and decrease when the commanded state is decreased.
2. 5: This step verifies that the control module is providing ground to the EVAP canister purge solenoid valve.
3. 6: This step tests if a ground is constantly being applied to the EVAP canister purge solenoid valve.

DTC P0443

This DTC tests the evaporative emission (EVAP) system for a restricted or blocked EVAP vent path. The control module commands the EVAP canister purge solenoid valve Open and the EVAP canister vent solenoid valve Closed. This allows vacuum to be applied to the EVAP system. Once a calibrated vacuum level has been reached, the control module commands the EVAP canister purge solenoid valve Closed and the EVAP canister vent solenoid valve Open. The control module monitors the fuel tank pressure (FTP) sensor for a decrease in vacuum. If the vacuum does not decrease to near 0 inches H2O in a calibrated time, this DTC sets.

The following table illustrates the relationship between the ON and OFF states, and the Open or Closed states of the EVAP canister purge and vent solenoid valves.

EVAP Canister Purge & Vent Solenoid Valves ON/OFF States

1. DTCs P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0147, P0151, P0152, P0153, P0154, P0155, P0157, P0158, P0160, P0161, P0167, P0220, P0442, P0443, P0449, P0452, P0453, P0455, P0502, P0503, P1111, P1112, P1114, P1115, P1120 are not set.
2. The ignition voltage is between 10-18 volts.
3. The barometric pressure (BARO) is more than 75 kPa.
4. The fuel level is between 15-85 percent.
5. The engine coolant temperature (ECT) is between 4-30°C (39-86°F).
6. The intake air temperature (IAT) is between 4-30°C (39-86°F).
7. The start up ECT and IAT are within 9°C (16°F) of each other.

1. The fuel tank pressure sensor is less than - 10 inches H2O.
2. The condition is present for as long as 30 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. An intermittent condition could be caused by a damaged EVAP vent housing, a temporary blockage at the EVAP canister vent solenoid valve inlet, or a pinched vent hose. A blockage in the vent system will also cause a poor fuel fill problem.
2. An EVAP canister, vent hose, or vent solenoid valve that has restricted flow may cause this DTC to set. Using purge solenoid valve command with a scan tool will allow vacuum to be applied to the system instead of pressure. With the EVAP canister vent solenoid valve open and the EVAP canister purge solenoid valve commanded to 100 percent, vacuum should not increase to more than 9 in H2O.
3. For intermittent conditions, refer to «Intermittent Conditions»(/chevrolet/chevy-express-g2500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-troubleshooting__intermittent-conditions) .

DTC P0446

A battery voltage is supplied to the evaporative emission (EVAP) canister vent solenoid valve. The control module grounds the EVAP canister vent solenoid valve control circuit to close the valve by means of an internal switch called a driver. The scan tool displays the commanded state of the EVAP canister vent solenoid valve as ON or OFF. The control module monitors the status of the driver. If the control module detects an incorrect voltage for the commanded state of the driver, this DTC sets.

The following table illustrates the relationship between the ON and OFF states, and the OPEN or CLOSED states of the EVAP canister vent solenoid valve.

EVAP Canister Vent Solenoid Valve ON/OFF States

1. The engine speed is more than 400 RPM.
2. The system voltage is between 6-18 volts.

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

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers on the diagnostic table.

1. 2: Listen for a click when the valve operates. Verify that both the ON and the OFF states are commanded.
2. 5: This step verifies that the control module is providing ground to the evaporative emission (EVAP) canister vent solenoid valve.
3. 6: This step tests if the EVAP canister vent solenoid valve control circuit is grounded.

DTC P0449

The fuel tank pressure (FTP) sensor measures the difference between the air pressure or vacuum in the evaporative emission (EVAP) system, and the outside air pressure. The control module supplies a 5-volt reference and a low reference circuit to the FTP sensor. The FTP sensor signal circuit voltage varies depending on EVAP system pressure or vacuum. If the FTP sensor signal voltage goes below a calibrated value, this DTC sets.

The following table illustrates the relationship between the FTP sensor signal voltage and the EVAP system pressure/vacuum.

FTP Sensor Signal Voltage vs EVAP System Pressure/Vacuum

The engine is running.

1. The FTP sensor voltage is less than 0.1 volts.
2. All conditions are present for more than 5 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers on the diagnostic table.

1. 5: This step tests for the proper operation of the circuit in the high voltage range.
2. 6: The 5-volt reference circuit for the FTP is routed through connector C152. This area may provide a good test point for diagnosing concerns with this circuit.
3. 7: The FTP sensor signal circuit is routed through connector C152. This area may provide a good test point for diagnosing concerns with this circuit.

DTC P0452

The fuel tank pressure (FTP) sensor measures the difference between the air pressure or vacuum in the evaporative emission (EVAP) system, and the outside air pressure. The control module supplies a 5-volt reference and a low reference circuit to the FTP sensor. The FTP sensor signal circuit voltage varies depending on EVAP system pressure or vacuum. If the FTP sensor signal voltage increases above a calibrated value, this DTC sets.

The following table illustrates the relationship between FTP sensor signal voltage and the EVAP system pressure/vacuum.

FTP Sensor Signal Voltage vs EVAP System Pressure/Vacuum

The engine is running.

1. The fuel tank pressure (FTP) sensor voltage is more than 4.9 volts.
2. All conditions are present for more than 5 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

The number below refers to the step number on the diagnostic table.

1. 2: If DTC P0641 or P0651 is set, the 5-volt reference circuit may be shorted to a voltage.

DTC P0453

The control module tests the evaporative emission (EVAP) system for a large leak. The control module monitors the fuel tank pressure (FTP) sensor signal to determine the EVAP system vacuum level. When the conditions for running are met, the control module commands the EVAP canister purge solenoid valve OPEN and the EVAP vent solenoid valve CLOSED. This allows engine vacuum to enter the EVAP system. At a calibrated time, or vacuum level, the control module commands the EVAP canister purge solenoid valve closed, sealing the system, and monitors the FTP sensor input in order to determine the EVAP system vacuum level. If the system is unable to achieve the calibrated vacuum level, or the vacuum level decreases too rapidly, this DTC sets.

The following table illustrates the relationship between the ON and OFF states, and the OPEN or CLOSED states of the EVAP canister purge and vent solenoid valves.

EVAP Canister Purge & Vent Solenoid Valves ON/OFF States

1. DTCs P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0147, P0151, P0152, P0153, P0154, P0155, P0157, P0158, P0160, P0161, P0167, P0220, P0442, P0443, P0449, P0452, P0453, P0502, P0503, P1111, P1112, P1114, P1115, P1120 are not set.
2. The engine is running.
3. The ignition voltage is between 10-18 volts.
4. The barometric pressure (BARO) is more than 75 kPa.
5. The fuel level is between 15-85 percent.
6. The engine coolant temperature (ECT) is between 4-65°C (39-149°F).
7. The intake air temperature (IAT) is between 4-75°C (39-167°F).
8. The start-up ECT and IAT are within 9°C (16°F) of each other.

The EVAP system is not able to achieve or maintain vacuum during the diagnostic test.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

1. To help locate intermittent leaks, use the J 41413-200 Evaporative Emissions System Tester (EEST) to introduce smoke into the EVAP system. Move all EVAP components while observing smoke with the J 41413-SPT High Intensity White Light. Introducing smoke in 15 second intervals will allow less pressure into the EVAP system. When the system is less pressurized, the smoke will sometimes escape in a more condensed manner.
2. A temporary blockage in the EVAP canister purge solenoid valve, purge pipe or EVAP canister could cause an intermittent condition. Inspect and repair any restriction in the EVAP system.
3. To improve the visibility of the smoke exiting the EVAP system, observe the suspected leak area from different angles with the J 41413-SPT .
4. Reviewing the Failure 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.
5. For intermittent conditions, refer to «Intermittent Conditions»(/chevrolet/chevy-express-g2500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-troubleshooting__intermittent-conditions) .

The numbers below refer to the step numbers on the diagnostic table.

1. 6: A normal operating FTP sensor should increase above 5 inches of H2O and stop between 6 inches of H2O and 7 inches of H2O.

DTC P0455

This DTC tests for undesired intake manifold vacuum flow to the evaporative emission (EVAP) system. The control module seals the EVAP system by commanding the EVAP canister purge solenoid valve Closed and the EVAP canister vent solenoid valve Closed. The control module monitors the fuel tank pressure (FTP) sensor to determine if a vacuum is being drawn on the EVAP system. If vacuum in the EVAP system is more than a predetermined value within a predetermined time, this DTC sets.

The following table illustrates the relationship between the ON and OFF states, and the Open or Closed states of the EVAP canister purge and vent solenoid valves.

EVAP Canister Purge & Vent Solenoid Valves ON/OFF States

1. DTCs P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0147, P0151, P0152, P0153, P0154, P0155, P0157, P0158, P0160, P0161, P0167, P0220, P0442, P0443, P0449, P0452, P0453, P0455, P0502, P0503, P1111, P1112, P1114, P1115, P1120 are not set.
2. The ignition voltage is between 10-18 volts.
3. The barometric pressure (BARO) is more than 75 kPa.
4. The fuel level is between 15-85 percent.
5. The engine coolant temperature (ECT) is between 4-30°C (39-86°F).
6. The intake air temperature (IAT) is between 4-30°C (39-86°F).
7. The start up ECT and IAT are within 9°C (16°F) of each other.

1. A continuous open purge flow condition is detected during the diagnostic test.
2. The fuel tank pressure decreases to less than -11 inches H2O.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

DTC P0496

The engine idle speed is controlled by the idle air control (IAC) valve. The IAC valve is on the throttle body. The IAC valve pintle moves in and out of an idle air passage bore to control air flow around the throttle plate. The IAC valve consists of a movable pintle, driven by a gear attached to an electric motor called a stepper motor. The stepper motor is capable of highly accurate rotation, or of movement, called steps. The stepper motor has 2 separate windings that are called coils. Each coil is supplied current by 2 circuits from the powertrain control module (PCM). When the PCM changes polarity of a coil, the stepper motor moves one step. The PCM uses a predetermined number of counts to determine the IAC pintle position. Observe IAC counts with a scan tool. The IAC counts will increment up or down as the PCM attempts to change the IAC valve pintle position. An IAC Reset will occur when the ignition key is turned OFF. First, the PCM will seat the IAC pintle in the idle air passage bore. Second, the PCM will retract the pintle a predetermined number of counts to allow for efficient engine start-up. If the engine idle speed is out of range for a calibrated period of time, an idle speed diagnostic trouble code (DTC) sets.

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0171, P0172, P0174, P0175, P0200, P0300, P0442, P0443, P0446, P0449, P0455, P0496, P1111, P1112, P1114, P1115, P1121, P1122, P1380, P1381are not set.
2. The Engine Run Time parameter is more than 60 seconds.
3. The ECT Sensor parameter is between 60-116°C (140-241°F).
4. The IAT Sensor parameter is more than -10°C (+14°F).
5. The TP Sensor parameter is less than 0.7 percent.
6. The BARO parameter is more than 65 kPa.
7. The Vehicle Speed Sensor parameter is less than 1.6 km/h (1 mph).
8. The Ignition 1 Signal parameter is between 9-18 volts.
9. The above conditions are met for more than 2 seconds.

The actual engine speed is 100 RPM less than the desired engine speed for more than 5 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

Inspect for the following conditions

1. High resistance in an IAC valve control circuit
2. Restricted air intake system
3. Proper operation and installation of all air intake components
4. Collapsed, clogged, or loose air intake ducts
5. A clogged air filter
6. Proper operation of the mass air flow (MAF) sensor, if equipped
7. A tampered with or damaged throttle stop screw
8. A tampered with or damaged throttle plate, throttle shaft, or throttle linkage
9. Objects blocking the IAC passage or throttle bore
10. Excessive deposits in the IAC passage or on the IAC pintle
11. Excessive deposits in the throttle bore or on the throttle plate
12. Vacuum leaks
13. A low or unstable idle condition could be caused by a non-IAC system problem that can not be overcome by the IAC valve-Refer to «Symptoms - Engine Controls»(/chevrolet/chevy-express-g2500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-troubleshooting) .

If the problem is determined to be intermittent, refer to Intermittent Conditions .

The numbers below refer to the step numbers on the diagnostic table.

1. 5: This test will determine the ability of the PCM and the IAC valve control circuits to control the IAC valve.
2. 7: This test will determine the ability of the PCM to provide the IAC valve control circuits with a ground. On a normal operating system, the test lamp should not flash while the IAC Counts are incrementing.

DTC P0506

The engine idle speed is controlled by the idle air control (IAC) valve. The IAC valve is on the throttle body. The IAC valve pintle moves in and out of an idle air passage bore to control air flow around the throttle plate. The IAC valve consists of a movable pintle, driven by a gear attached to an electric motor called a stepper motor. The stepper motor is capable of highly accurate rotation, or of movement, called steps. The stepper motor has 2 separate windings that are called coils. Each coil is supplied current by 2 circuits from the powertrain control module (PCM). When the PCM changes polarity of a coil, the stepper motor moves one step. The PCM uses a predetermined number of counts to determine the IAC pintle position. Observe IAC counts with a scan tool. The IAC counts will increment up or down as the PCM attempts to change the IAC valve pintle position. An IAC Reset will occur when the ignition key is turned OFF. First, the PCM will seat the IAC pintle in the idle air passage bore. Second, the PCM will retract the pintle a predetermined number of counts to allow for efficient engine start-up. If the engine idle speed is out of range for a calibrated period of time, an idle speed diagnostic trouble code (DTC) sets.

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0171, P0172, P0174, P0175, P0200, P0300, P0442, P0443, P0446, P0449, P0455, P0496, P1111, P1112, P1114, P1115, P1121, P1122, P1380, P1381are not set.
2. The Engine Run Time parameter is more than 60 seconds.
3. The ECT Sensor parameter is between 60-116°C (140-241°F).
4. The IAT Sensor parameter is more than -10°C (+14°F).
5. The TP Sensor parameter is less than 0.7 percent.
6. The BARO parameter is more than 65 kPa.
7. The Vehicle Speed Sensor parameter is less than 1.6 km/h (1 mph).
8. The Ignition 1 Signal parameter is between 9-18 volts.
9. The above conditions are met for more than 2 seconds.

The actual engine speed is 200 RPM more than the desired engine speed for more than 5 seconds.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

Inspect for the following conditions

1. High resistance in an IAC valve control circuit
2. The correct positive crankcase ventilation (PCV) valve, properly installed and proper operation of the PCV valve
3. Proper operation and installation of all air intake components
4. Proper installation and operation of the mass air flow (MAF) sensor, if equipped
5. A tampered with or damaged throttle stop screw
6. A tampered with or damaged throttle plate, throttle shaft, throttle linkage, or cruise control linkage, if equipped
7. A skewed high TP sensor
8. Excessive deposits in the IAC passage or on the IAC pintle
9. Excessive deposits in the throttle bore or on the throttle plate
10. Vacuum leaks
11. A high or unstable idle condition could be caused by a non-IAC system problem that can not be overcome by the IAC valve. Refer to «Symptoms - Engine Controls»(/chevrolet/chevy-express-g2500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-troubleshooting) .
12. If the problem is determined to be intermittent, refer to «Intermittent Conditions»(/chevrolet/chevy-express-g2500/1996-2012/remont/testing-diagnostics/#engine-control-system-43l-troubleshooting__intermittent-conditions) .

The numbers below refer to the step numbers on the diagnostic table.

1. 5: This test will determine the ability of the PCM and IAC valve control circuits to control the IAC valve.
2. 7: This test will determine the ability of the PCM to provide the IAC valve control circuits with a ground. On a normally operating system, the test lamp should not flash while the IAC Counts are incrementing.

DTC P0507

Description

This diagnostic applies to internal microprocessor integrity conditions within the powertrain control module (PCM). This diagnostic also addresses if the PCM is not programmed.

The number below refers to the step number on the diagnostic table.

1. 2: A DTC P0602 indicates the PCM is not programmed.

DTC P0601-P0607, P1600, P1621, P1627, P1680, P1681, P1683, or P2610

See also:
• Engine Controls Schematics
• Engine Controls Connector End Views
• Powertrain Control Module (PCM) Connector End Views
• Diagnostic System Check - Engine Controls
• Scan Tool Data List
• Intermittent Conditions
• Circuit Testing
• Wiring Repairs
• Testing for Intermittent Conditions and Poor Connections
• Connector Repairs
• Powertrain Control Module (PCM) Replacement
• Diagnostic Trouble Code (DTC) List
• Fuel System Diagnosis
• Symptoms - Engine Mechanical
• DTC P0101
• Engine Cover Replacement
• Probing Electrical Connectors
• Symptoms - Hydraulic Brakes
• Vibration Analysis - Driveline
• CKP System Variation Learn Procedure
• Ground Distribution Schematics
• Restricted Exhaust
• Spark Plug Wire Inspection
• Spark Plug Inspection
• Distributor Inspection
• Measuring Frequency
• Testing for Continuity
• Testing for Short to Ground
• Testing for a Short to Voltage
• Repairing Connector Terminals
• Testing for Electrical Intermittents
• Inducing Intermittent Fault Conditions
• Using Connector Test Adapters
• Exhaust Leakage
• Troubleshooting with a Test Lamp
• Lifting and Jacking the Vehicle
• Service Programming System (SPS)
• DTC P0420 or P0430