Strange Codes

[drumset5994]

So my dad's 2002 GMC Sierra with the 4.3L V6 started misfiring real bad. Flashing Service Engine Soon Light. Pulled the codes.

 

P0101---MAF Sensor Circuit Malfunction

P0304---Cylinder 4 Misfire Detected

 

 

I've been doing a little research, trying to see what could be one of many causes. It ranges from many things like moisture on the distributor, to possible cylinder 4 injector failure. I just figured i'd ask the opinion of others here...incase its happened to anyone else.

 

I checked the wires...seemed good. I also checked the MAF sensor...connection in tact, working.

 

He's taking it in in a day or so...just looking for some ideas.

[2500ak]

First thing to do when it throws a MAF code is clean the MAF.

[jrrod2004]

Here is some reading information:

 

 

 

 

 

 

Service Information

2002 GMC Truck GMC C Sierra - 2WD | Sierra, Silverado (VIN C/K) Service Manual | Document ID: 1489128 #PI01624A: Service VME - 4.8 5.3 6.0 LM4 LM7 LR4 LQ4 LQ9 GEN III Engines with MAF Sensor Code P0101 - kw driveability fluctuation idle intermittent MAP rough stall surge hesitation - (Apr 5, 2004)

Subject:Service VME - 4.8 5.3 6.0 LM4 LM7 LR4 LQ4 LQ9 GEN III Engines with MAF Sensor Code P0101

 

 

Models:.

 

 

When servicing the vehicle with the VIN you entered, the following diagnosis might be helpful if the vehicle exhibits the described symptoms.

 

SERVICE VME

This message applies to all 1999 through 2004 Chevrolet, GMC, Olds, Buick and Cadillac pick-ups and utilities that are equipped with either the 4.8 liter, 5.3 liter or 6.0 liter Gen 3 V-8 engines. Recent warranty analysis indicates that both the MAF, or mass airflow sensor, and the MAP, or manifold absolute pressure sensor, are being replaced for a MAF sensor code P0101. The cause may actually be a MAP sensor failure causing the MAF sensor code. One of the MAP sensor’s primary functions is the calculation of the speed density formula, which is compared to the MAF sensor reading. Should the MAP sensor fail, the PCM may interpret this as a MAF sensor concern and set a P0101 code. If diagnostics are followed thoroughly the technician may find a MAP sensor failure causing this condition. In conclusion, when a MAF sensor code of P0101 is found the technician needs to verify the proper operation of the MAP sensor before concluding that the MAF sensor requires replacement.

 

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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. This diagnostic approach was developed for the vehicle with the VIN you entered and should not be automatically be used for other vehicles with similar symptoms.

 

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MODELS:

 

(00-04 Chevrolet Silverado Truck C1,C2,C3) and (00-04 Chevrolet Tahoe C1,C2,C3) and (00-04 Chevrolet Suburban C1,C2,C3) and (00-04 GMC Sierra Truck C1,C2,C3) and (00-04 GMC Yukon C1, C2, C3) and (00-04 GMC Yukon XL C1, C2 C3) and (02-04 Cadillac, Escalade, C6) and (03-04 Cadillac, EXT, C1) and (02-043 Chevrolet, Avalanche, K1, K2) and (02-04 Chevrolet Silverado Truck K1, K2, K3) and (02-04 GMC Sierra Truck K1, K2, K3) and (02-04 Chevrolet Tahoe, K1, K2, K3) and (02- 04 Chevrolet Suburban, K1, K2, K3) and (03 Chevrolet Camaro) and (02-04 Chevrolet Corvette) and (03 Pontiac Firebird) and (02-04 GMC, Yukon, K1, K2, K3) and (02-04 GMC, Yukon XL, C1,C2, C3) and (00-04 GMC, Yukon XL, K1, K2, K3) and (03-04 GMC S1 T1) and (03-04 Chevrolet S1 T1) and (03-04 Chevrolet Express G1, G2) and (03-04 GMC Savana G1, G2)

 

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GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

 

 

WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION

 

 

© 2008 General Motors Corporation. All rights reserved.

[jrrod2004]

Service Information

 

2002 GMC Truck GMC C Sierra - 2WD | Sierra, Silverado (VIN C/K) Service Manual | Document ID: 796199 DTC P0101

Circuit Description

The mass air flow (MAF) sensor is an air flow meter that measures the amount of air entering the engine. The powertrain control module (PCM) uses the MAF sensor signal in order to provide the correct fuel delivery for a wide range of engine speeds and loads. A small quantity of air entering the engine indicates a deceleration or idle. A large quantity of air entering the engine indicates an acceleration or high load condition. The MAF sensor has an ignition 1 voltage circuit, a ground circuit, and a signal circuit. The PCM applies a voltage to the sensor on the signal circuit. The sensor uses the voltage in order to produce a frequency based on inlet air flow through the sensor bore. The frequency varies within a range of around 2,000 Hertz at idle to about 10,000 Hertz at maximum engine load. The PCM uses the following sensor inputs in order to calculate a predicted MAF value:

 

 

• The manifold absolute pressure (MAP)

 

 

• The intake air temperature (IAT)

 

 

• The engine speed (RPM)

 

The PCM compares the actual MAF sensor frequency signal to the predicted MAF value. This comparison will determine if the signal is stuck based on a lack of variation, or is too low or too high for a given operating condition. DTC P0101 sets if the actual MAF sensor frequency signal is not within a predetermined range of the calculated MAF value.

 

Conditions for Running the DTC

 

• DTCs P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0121, P0122, P0123, P0335, P0336, P0401, P0440, P0442, P0443, P0446, P0449, P1106, P1107, P1111, P1112, P1121, P1122, or P1441 are not set.

 

 

• The engine is running.

 

 

• The ignition 1 signal is between 11 volts and 18 volts.

 

 

• The throttle position (TP) sensor angle is less than 95 percent.

 

 

• The change in the TP sensor angle is less than 5 percent.

 

 

• The MAP sensor is less than 80 kPa.

 

 

• The change in the MAP sensor is less than 3 kPa.

 

 

• The above conditions are met for 1.5 seconds.

 

Conditions for Setting the DTC

The PCM detects that the actual MAF sensor frequency signal is not within a predetermined range of the calculated MAF value for more than 4.0 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.

 

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

Inspect for the following conditions:

 

 

• An incorrectly routed harness--Inspect the harness of the MAF sensor in order to verify that it is not routed too close to the following components:

 

 

- The secondary ignition wires or coils

 

 

- Any solenoids

 

 

- Any relays

 

 

- Any motors

 

 

• The throttle plate for sticking, or for deposits on the throttle plate or in the throttle bore

 

 

• A low minimum air rate through the sensor bore may cause this DTC to set at idle or during deceleration. Inspect for any vacuum leaks downstream of the MAF sensor.

 

 

• A wide open throttle acceleration from a stop should cause the MAF sensor g/s display on the scan tool to increase rapidly. This increase should be from 6-12 g/s at idle to 130 g/s or more at the time of the 1-2 shift. If the increase is not observed, inspect for a restriction in the induction system or the exhaust system.

 

 

• The barometric pressure that is used in order to calculate the predicted mass air flow value is initially based on the MAP sensor at key ON. When the engine is running, the MAP sensor value is continually updated near wide open throttle. A skewed MAP sensor will cause the calculated mass air flow value to be inaccurate. The value shown for the MAP sensor display varies with the altitude. With the ignition ON and the engine OFF, 103 kPa is the approximate value near sea level. This value will decrease by approximately 3 kPa for every 305 meters (1,000 feet) of altitude.

 

 

• A high resistance on the ground circuit of the MAP sensor may cause this DTC to set.

 

 

• Any loss of vacuum to the MAP sensor may cause this DTC to set.

 

 

• A high resistance in the ignition voltage circuit of the MAF sensor may cause this DTC to set.

 

If you suspect the condition may be related to aftermarket accessories, refer to Checking Aftermarket Accessories in Wiring Systems.

 

If the condition is intermittent, refer to Intermittent Conditions .

 

Test Description

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

 

 

1. This step will determine if the MAP sensor voltage is within the proper range at idle.
   
2. This step will determine if the MAP sensor responds properly to the change in manifold pressure.
   
3. This step will determine if the throttle position (TP) sensor is operating properly.
   
4. This step will determine if any mechanical faults have caused this DTC to set.
   

Step

 

Action

 

Values

 

Yes

 

No

 

Schematic Reference: Engine Controls Schematics

 

1

 

Did you perform the Diagnostic System Check-Engine Controls ?

 

--

 

Go to Step 2

 

Go to Diagnostic System Check - Engine Controls

 

2

 

 

1. Start the engine.
   
2. Monitor the Diagnostic Trouble Code (DTC) Information with the scan tool.
   

Does the scan tool display any other DTCs set?

 

--

 

Go to Diagnostic Trouble Code (DTC) List

 

Go to Step 3

 

3

 

 

1. Observe the Freeze Frame/Failure Records data for this DTC.
   
2. Turn OFF the ignition for 30 seconds.
   
3. Start the engine.
   
4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text or as close to the Freeze Frame/Failure Records data that you observed.
   

Does the DTC fail this ignition?

 

--

 

Go to Step 4

 

Go to Diagnostic Aids

 

4

 

 

1. Allow the engine to reach operating temperature.
   
2. Observe the MAP sensor voltage with a scan tool .
   

Is the MAP sensor voltage within the specified range?

 

0.8-4 V

 

Go to Step 5

 

Go to DTC P0106

 

5

 

 

1. Idle the engine.
   
2. Observe the MAP sensor kPa with a scan tool.
   
3. Increase the engine speed slowly to 3,000 RPM and then back to idle.
   

Does the MAP sensor kPa change smoothly and gradually through the specified range of the test?

 

--

 

Go to Step 6

 

Go to DTC P0106

 

6

 

Important:: If the vehicle is equipped with throttle actuator control (TAC), proceed to the next step.

 

 

1. Turn OFF the ignition.
   
2. Turn ON the ignition, with the engine OFF.
   
3. Observe the TP sensor angle from closed throttle to wide open throttle.
   
4. Depress completely and then release the accelerator pedal.
   

Does the scan tool indicate that the TP sensor angle changed smoothly and completely through the specified range of the test?

 

0-100%

 

Go to Step 7

 

Go to DTC P0121

 

<a href="http://gsi.xw.gm.com/si/showDoc.do?docSyskey=796199&pubCellSyskey=28592&pubObjSyskey=796199&from=sm&cellId=28592#TD07">7

 

Inspect for the following conditions:

 

 

• A restricted air intake duct

 

 

• A collapsed air intake duct

 

 

• A misaligned air intake duct

 

 

• A dirty air filter element

 

 

• A deteriorating air filter element

 

 

• Any objects blocking the air inlet screen of the MAF sensor

 

 

• Any debris on the sensing elements of the MAF sensor

 

 

• Any vacuum leak downstream of the MAF sensor

 

 

• A poor vacuum connection at the MAP sensor

 

 

• A restricted exhaust system

 

Did you find and correct the condition?

 

--

 

Go to Step 10

 

Go to Step 8

 

8

 

Test for an intermittent and for a poor connection at the MAF sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

 

Did you find and correct the condition?

 

--

 

Go to Step 10

 

Go to Step 9

 

9

 

Replace the MAF/ IAT sensor. Refer to Mass Airflow Sensor/Intake Air Temperature Sensor Replacement .

 

Did you complete the replacement?

 

--

 

Go to Step 10

 

--

 

10

 

 

1. Use the scan tool in order to clear the DTCs.
   
2. Turn OFF the ignition for 30 seconds.
   
3. Start the engine.
   
4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
   

Does the DTC run and pass?

 

--

 

Go to Step 11

 

Go to Step 2

 

11

 

With a scan tool, observe the stored information, Capture Info.

 

Does the scan tool display any DTCs that you have not diagnosed?

 

--

 

Go to Diagnostic Trouble Code (DTC) List

 

System OK

 

© 2008 General Motors Corporation. All rights reserved.