DTC P0102 MAF or VAF Circuit Low Input


GMC97
08-20-2004, 05:50 PM
I have a 1997 GMC Sierra 4x4 with the 5.7L engine.

I had the Fuel Pump and MAP replaced (truck quit) and since then I ahave been getting a "Check Engine Soon" Lite with the P0102 code.

I have replaced the MAF with two rebuilt ones from Discount Auto and three from the junk yard, with no luck. I have also replaced the PCV, air filter, plugs, rotor, rotor cap, and wires.

I am out of ideas.

Any help

maintainin76
08-20-2004, 08:37 PM
Might want to start looking for some faulty wiring or connections. Here is the checkout procedure from my Haynes repair manual. There is a paragraph before this one telling how to check the MAF sensor itself, but since I doubt that is your problem I left it out(plus you gotta have a scan tool).

Before checking the MAF sensor operation, check the voltage supply and ground circuits. Disconnect the electrical connector from the MAF sensor and connect the positive lead of a voltmeter to the pink wire terminal and the negative lead to the black/white wire terminal at the harness connector. Turn the ignition key ON-the voltage should read approximately 12 volts. If the voltage is incorrect, check the circuits from the MAP(***This is what it says in the manual, but I'm not sure if it is a typo and meant MAF instead since I cant think of what the MAP would have to do with the MAF, especially as far as supply voltage is concerned. I inlcuded the MAP checkout below just in case it wasnt a typo***) sensor to the power distribution center and engine ground point(dont forget to check the fuses first).

If you dont get that 12 volts, here is the checkout for the MAP sensor. But as I stated in bold above,this might not be the problem. Especially since the MAP has its own trouble codes(P0105-0109).

NOTE: Performing the following test will set a diagnostic trouble code and illuminate the Service Engine Soon light. Clear the diagnostic trouble code after performing tests and making necessary repairs.

The Map sensor is located on the upper intake manifold plenum. Check the terminals in the connector and wires leading to the sensor for looseness and breaks. Before checking the MAP sensor, check the voltage supply and ground circuits from the ECM/PCM. Disconnect the electrical connector from the MAP sensor and connect the positive lead of a voltmeter to the grey wire terminal and the negative lead to the orange/black or black wire terminal at the harness connector. Turn the igniton key ON-the voltage should read approximatley 5.0 volts. If the voltage is incorrect, check the wiring from the MAP sensor to the ECM/PCM. If the circuits are good, have the ECM/PCM checked at a dealer service department or other properly equipped repair facility.

To check MAP sensor operation, reconnect the connector to the MAP sensor and using a suitable probe, backprobe the light green wire terminal of the MAP sensor connector. Connect the positive lead of a voltmeter to the probe and the negative lead to a good engine ground point. Turn the igniton key ON- with the engine not running the voltage should read 4.0 to 5.0 volts. Start the engine and allow it to idle-the voltage should decreas to approximately .5 to 2.0 volts. If the test results are incorrect, replace the MAP sensor.

Hope this checkout helps. Especially after I typed all that!!!! :lol2:

Be on the lookout for bad wires and loose connections. Good luck.

rpm4kt
01-30-2008, 08:56 PM
The MAP controls the voltage to all the air intake scensors and controls the air to fule mixture so there for would be directly conected to the MAF. Just went through the same prob with my car. RPM

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