Diagnostic Codes

rws · December 23, 2004

'05 Silverado Crew 5.3L 4800 miles

Check Engine light came on and had rough idle. Took it to dealer and Warranty Invoice said truck had error codes P0151 and P0300. They replaced Oxygen Sensor and truck runs good. What exactly do those two error codes indicate/mean?

tia

sperry · December 23, 2004

DTC P0131 or P0151

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. If the PCM detects an HO2S voltage that stays below a specified value, DTCs P0131 or P0151 will set.

Conditions for Running the DTC

* Lean Test Enable: DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0169, P0178, P0179, P0200, P0220, P0300, P0442, P0446, P0452, P0453, P0455, P0496, P1125, P1258, P1514, P1515, P1516, P1518, P2108, P2135 are not set.

* The Loop Status parameter is closed.

* The Ignition 1 Signal parameter is between 10-18 volts.

* The Fuel Alcohol Content parameter is less than 90 percent.

* The Fuel Tank Level Remaining parameter is more than 10 percent.

* The TP Indicated Angle parameter is between 3-70 percent more than the value observed at idle.

OR

* Power Enrichment Test Enable: DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0169, P0178, P0179, P0200, P0220, P0300, P0442, P0446, P0452, P0453, P0455, P0496, P1125, P1258, P1514, P1515, P1516, P1518, P2108, P2135 are not set.

* The Loop Status parameter is closed.

* The Ignition 1 Signal parameter is between 10-18 volts.

* The Fuel Alcohol Content parameter is less than 90 percent.

* The Fuel Tank Level Remaining parameter is more than 10 percent.

* The Engine Run Time parameter is more than 30 seconds.

* The Power Enrichment parameter is active for more than 2 seconds.

Conditions for Setting the DTC

Lean Test:

The PCM detects that the affected HO2S voltage parameter is less than 200 mV for 165 seconds.

or

Power Enrichment Test:

The PCM detects that the affected HO2S voltage parameter is less than 400 mV for 10 seconds.

Action Taken When the DTC Sets

* The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

* 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.

* The control module commands the Loop Status open.

Conditions for Clearing the MIL/DTC

* The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

* A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

* A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

* Clear the MIL and the DTC with a scan tool.

sperry · December 23, 2004

DTC P0300

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.

Conditions for Running the DTC

* DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0116, P0117, P0118, P0125, P0128, P0220, P0315, P0335, P0336, P0341, P0342, P0343, P0502, P0503, P1114, P1115, P1120, P1258 are not set.

* The engine speed is between 450-5,000 RPM.

* The ignition voltage is between 10-18 volts.

* The engine coolant temperature (ECT) is between -7 and +130°C (+19 and +266°F).

* The fuel level is more than 10 percent.

* The throttle angle is steady within 1 percent.

* The antilock brake system (ABS) and the traction control system are not active.

* The transmission is not changing gears.

* The A/C clutch is not changing states.

* The PCM is not in fuel shut-off or decel fuel cut-off mode.

* The PCM is not receiving a rough road signal.

Conditions for Setting the DTC

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

Action Taken When the DTC Sets

* The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

* 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

* The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

* A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

* A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

* Clear the MIL and the DTC with a scan tool.

Diagnostic Aids

* Excessive vibration from sources other than the engine could cause DTC P0300 to set. The following are possible sources of vibration:

o Thickness variation of the brake rotors--Refer to Symptoms - Hydraulic Brakes in Hydraulic Brakes.

o The drive shaft not balanced--Refer to Vibration Analysis - Driveline in Vibration Diagnosis and Correction.

o Worn or damaged accessory drive belt--Refer to Symptoms - Engine Mechanical in Engine Mechanical-4.8L, 5.3L and 6.0L

* There may be more or less cylinders actually misfiring than indicated by the scan tool.

* Spray water on the secondary ignition components using a spray bottle. Look and listen for arcing or misfiring.

* If there are multiple misfires on only one bank, inspect the fuel injector and ignition coil, power and ground circuits for that bank. Refer to Engine Controls Schematics .

sperry · December 23, 2004

Info - Misfire DTCs P0300, P1380, P1381 and Catalytic Converter Damage Due to Installation of Alarm Systems #02-06-05-004A - (Jan 9, 2004)

Misfire DTCs P0300, P1380, P1381 and Catalytic Converter Damage Due to Installation of Alarm Systems

2004 and Prior GM Passenger Cars and Light Duty Trucks

2003-2004 HUMMER H2

2004 and Prior Isuzu Light Duty Trucks

This bulletin is being revised to add the 2004 model year and include specific DTCs in the title line. Please discard Corporate Bulletin Number 02-06-05-004 (Section 06 - Engine/Propulsion System).

General Motors Engineering, in an effort to determine the root cause of catalytic converter damage, has determined that aftermarket alarm systems incorrectly installed in vehicles have the potential to cause misfire codes and damage to the converter. These alarm systems use a circuit interrupt which utilizes the ignition circuit on the vehicles.

These alarm systems utilize mechanical relays and normal vehicle movement can trigger these relays to engage and disengage the ignition circuit while the vehicle is in motion. These disruptions of the ignition circuit, which occur in milliseconds, may cause more fuel to be commanded. Over time, this dumping of fuel on and off again can cause misfire codes and ultimately damage the converter assembly.

Important

Engineering could not identify any alarms that utilize solid state circuitry that would eliminate this concern. Because of this, it has been determined that all alarm systems must be routed through the starter circuit in order to avoid this condition.

Dealers must be aware of this issue and take note of the wiring on vehicles with alarm systems that come in for repair, particularly for catalytic converter damage that seem to have no known root cause.

sperry · December 23, 2004

97-05 Vehicles with 4.8 5.3 5.7 and 6.0 Gen III V8 Engines and Misfires on One Bank - kw CEL diagnostics driveability DTC P0171 P0172 P0174 P0175 P0300 P0301 P0302 P0303 P0304 P0305 P0306 P0307 P0308 #PIP3056 - (Jul 12, 2004)

97 - 05 Vehicles with 4.8 5.3 5.7 and 6.0 Gen III V8 Engines and Misfires On One Bank

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The following diagnosis might be helpful if the vehicle exhibits the described symptoms in the PI.

Condition/Concern:

Check Engine Light with a P0300 due to 2 - 4 cylinders misfiring on the same bank of the engine. DTCs P0171, P0172, P0174 or P0175 may also set for the misfiring bank.

Recommendation/Instructions:

If the published misfire diagnostic does not isolate the cause, perform the following suggestions as necessary:

1. Perform a fuel injector balance test for all 8 cylinders. If a fuel injector concern exists, it is possible to misfuel an entire bank of the engine, causing multiple cylinders on the same bank to misfire even though the root cause is a single fuel injector.

2. Inspect O2 sensor connections on the misfiring bank for corrosion or water intrusion. If water intrusion is found on the right bank, it may be due to the AC Evaporator Condensation dripping onto the O2 sensor harness. If this condition is found, reposition and shield the harness to prevent a repeat concern and repair the connections.

3. Check for excessive exhaust backpressure using the restricted exhaust diagnosis from SI.

4. Swap the Position 1 O2 sensors side to side to see if the misfires move to the other bank of the engine. If so, replace the O2 sensor.

.

Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance.

Models:

(00 - 05 Cadillac Escalade - C6 and K6) and (02 - 05 Chevrolet Avalanche - C1, C2 K1 and K2) and (99 - 05 Chevrolet Silverado - C1, C2 K1 and K2) and (00 - 05 Chevrolet Suburban - C1, C2, K1 and K2) and (00 - 05 Chevrolet Tahoe - C1 and K1) and (99 - 05 GMC Sierra C1, C2 K1 and K2) and (00 - 05 GMC Yukon - C1, C2, K1 and K2) and (03 - 05 Chevrolet Express G1, G2, G3, H1, H2 ) and (03 - 05 GMC Savana G1, G2, G3, H1, H2 ) and (04 - 05 Buick Rainier S1, T1 ) and (03 - 05 Chevrolet Trail Blazer EXT S1, T1 ) and (03 - 05 GMC Envoy XL XUV S1, T1 ) and (03 - 05 Hummer H2) and (04 - 05 Cadillac CTS-V DB) and (98 - 02 Chevrolet Camaro FB) and (97 - 04 Chevrolet Corvette YB) and (98 - 02 Pontiac Firebird FB) and (04 - 05 Pontiac GTO VB)

sperry · December 23, 2004

99-03 GEN III Engine Misfire at Idle Cold and Possible P0171 and/or P0174 -kw 4.8 5.3 6.0 LR4 LM4 LM7 LQ4 crack air hesitate intermittent internal intake leak lean miss power rough surge vacuum P0300 #PIP3232 - (Nov 15, 2004)

99-03 GEN III Engine Misfire at Idle Cold and Possible P0171 and/or P0174

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The following diagnosis might be helpful if the vehicle exhibits the symptom described in the PI.

Condition/Concern:

99 through 03 GEN III truck engines may experience any of the following:

1. A cold rough idle that diminishes as the engine warms up.

2. Possible DTCs P0171, P0174, or P0300.

3. Random misfires at idle.

Recommendation/Instructions:

Check for leaking intake manifold seals around the intake ports. The intake gasket seals may be leaking around the intake ports, causing a lean condition. Many times they will leak around the bottom side of the port, making it a challenge to detect the vacuum leak. The technician may also note lower than normal MAF readings if the seals are leaking around the ports. If leaking intake gasket seals are found, they should be replaced. The intake plenum should also be checked for warpage that may cause an uneven clamping pressure of the seal. If the plenum is found to be warped, it will need to be replaced with new seals. Intake Manifold Cylinder Head Deck Flatness specifications are located in SI.

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Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance.

Models:

(99 00 01 02 03 C1 C2 C3 K1 K2 K3 LR4 LM4 LM7 LQ4 LQ9 Chevrolet Silverado Tahoe Suburban Avalanche Express Trailblazer ) and (99 00 01 02 03 C1 C2 C3 K1 K2 K3 LR4 LM4 LM7 LQ4 LQ9 GMC Sierra Savana Yukon Denalli Envoy) and (02 03 K6 K7 K8 Cadillac Escalade) and (03 Hummer N2).

Whew!