Mechanics

MAF SENSOR

2002 Chevrolet Silverado • V8 4WD Automatic • 170,779 miles

I had a rough starting when cold issue. Checked the codes and discovered two codes for a lean condition in both banks. After not finding a vac leak, I replaced the MAF with a remanufactured one. After replacing it, the truck started up when cold and the two codes went away. Now I have a PO-102 code. (Low voltage MAF) I checked for leaks around the sensor and along the ducted, and the wiring, no issues found. Could the new sensor be bad?
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Cdrew
December 18, 2010.



DTC P0102: MAF SENSOR CIRCUIT - LOW FREQUENCY

Description

Conditions For Running DTC

•The engine is running for more than 3 seconds. •The engine speed is more than 400 RPM. •The ignition 1 signal is more than 8 volts.

Conditions For Setting DTC

Action Taken When DTC Sets

Conditions For Clearing MIL/DTC

To locate components, see COMPONENT LOCATIONS. For circuit reference, see WIRING DIAGRAMS article. For connector terminal identification, see CONNECTOR IDENTIFICATION.

The PCM detects that the MAF sensor frequency signal is less than 1300 Hz for more than 1.2 seconds.

•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 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.

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. DTC P0102 sets if the PCM detects a frequency signal lower than the possible range of a properly operating MAF sensor.

SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L -2002 Chevrolet Silverado 1500
Test Description

The numbers below refer to the step numbers in the diagnostic procedures.

Diagnostic Procedures

5 This step will determine if any mechanical faults have caused this DTC to set.

10 This step tests the signal circuit of the MAF sensor for a short to another 5-volt reference circuit.

16 This step verifies that the signal circuit is not shorted to any other PCM circuit.

•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.

9 This step verifies the signal circuit from the MAF sensor electrical connector to the PCM. A voltage reading of less than 4 volts or more than 6 volts indicates a malfunction in the wiring or a poor connection.

1. Did you perform the Diagnostic System Check-Engine Controls? If yes, go to next step. If no, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM.

2. Start the engine. Observe the MAF sensor frequency with a scan tool. Is the MAF sensor frequency less than 1300 Hz? If yes, go to step 4. If no, go to next step.

3. Observe the Freeze Frame/Failure Records data for this DTC. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running DTC or as close to the Freeze Frame/Failure Records data that you observed. Does the DTC fail this ignition? If yes, go to next step. If no, see DIAGNOSTIC AIDS.

4. Observe the MAF sensor frequency with a scan tool. Move the harness and the connector of the MAF/IAT sensor. Does the movement of the harness or the connector affect the MAF sensor frequency? If yes, go to step 25. If no, go to next step.

5. Turn OFF the ignition. Inspect for the following conditions: •A restricted air intake duct.

•A collapsed air intake duct.

•A dirty air filter element.

•A deteriorating air filter element.

•Any unmetered air that enters the engine downstream of the MAF sensor.

SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L -2002 Chevrolet Silverado 1500
Did you find and correct the condition? If yes, go to step 30. If no, go to next step.

Does the DMM indicate continuity? If yes, go to next step. If no, go to step 20.

14. Test for continuity from the signal circuit of the MAF sensor to ground. Does the DMM indicate continuity? If yes, go to step 21. If no, go to step 16.

Disconnecting the PCM connectors may eliminate the short to voltage if the signal circuit is shorted to another PCM circuit.

6. Inspect the fuse in the ignition 1 voltage circuit of the MAF sensor. Is the fuse open? If yes, go to step 12. If no, go to next step.

7. Disconnect the harness connector of the MAF/IAT sensor. Turn ON the ignition, with the engine OFF. Connect a test lamp between the ignition 1 voltage circuit of the MAF sensor and a good ground. Does the test lamp illuminate? If yes, go to next step. If no, go to step 18.

8. Connect a test lamp between the ignition 1 voltage circuit of the MAF sensor and the ground circuit of the MAF sensor. Does the test lamp illuminate? If yes, go to next step. If no, go to step 19.

9. Measure the voltage from the signal circuit of the MAF sensor to a good ground. Is the voltage near 5 V? If yes, go to next step. If no, go to step 11.

10. Connect a 3-amp fused jumper wire between the signal circuit of the MAF sensor and a good ground. Start the engine. Do any additional DTCs set? If yes, go to step 23. If no, go to step 26.

11. Is the voltage less than 4.5 V? If yes, go to step 13. If no, go to step 15.

The ignition 1 voltage circuit of the MAF sensor is spliced to other components of the vehicle.

12. Test for continuity between the ignition 1 voltage circuit of the MAF sensor and ground. Does the Digital Multimeter (DMM) indicate continuity? If yes, go to step 17. If no, go to step 26.

13. Turn OFF the ignition. Disconnect the PCM. Test the signal circuit between the PCM and the MAF sensor for the following conditions: •A high resistance.

•An open circuit.

15. Turn OFF the ignition. Disconnect the PCM. Turn ON the ignition, with the engine OFF. Measure the voltage from the signal circuit of the MAF sensor to a good ground. Is the voltage near 0.0 V? If yes, go to next step. If no, go to step 22.

16. Test for continuity at the harness connector of the PCM from the signal circuit of the MAF sensor to all other circuits at both PCM connectors. Does the DMM indicate continuity between any other circuit? If yes, go to step 24. If no, go to step 27.

17. Repair the short to ground in the ignition 1 voltage circuit of the MAF sensor. Replace the fuse if necessary. After repairs, go to step 30.

18. Repair the open in the ignition 1 voltage circuit of the MAF sensor. After repairs, go to step 30.

19. Repair the high resistance or an open in the ground circuit of the MAF sensor. After repairs, go to step 30.

20. Repair the high resistance or an open in the signal circuit of the MAF sensor. After repairs, go to step 30.

21. Repair the short to ground in the signal circuit of the MAF sensor. After repairs, go to step 30.

22. Repair the short to voltage in the signal circuit of the MAF sensor. After repairs, go to step 30.

23. Repair the short between the signal circuit of the MAF sensor and the circuit for which the DTC set. After repairs, go to step 30.

24. Repair the circuits that are shorted together. After repairs, go to step 30.

25. Repair the harness or the connections as needed. After repairs, go to step 30.

26. Test for an intermittent and for a poor connection at the MAF/IAT sensor. Did you find and correct the condition? If yes, go to step 30. If no, go to step 28.

27. Test for an intermittent and for a poor connection at the PCM. Did you find and correct the condition? If yes, go to step 30. If no, go to step 29.

28. Replace the MAF/IAT sensor. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step 30.

29. Replace the PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Reprogram PCM. See POWERTRAIN CONTROL MODULE under PROGRAMMING. After repairs, go to next step.

30. Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running DTC. Does the DTC run and pass? If yes, go to next step. If no, go to step 2.

31. Observe the stored information, Capture Info with a scan tool. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS. If no, system is okay.

1. 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.

2.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.

3.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.

Condition may be related to aftermarket accessories.

Obxautomedic
Dec 18, 2010.