With PFI

Code 34 Chart:

Code 34 Wiring Diagram:

CIRCUIT DESCRIPTION:

The Manifold Absolute Pressure (MAP) sensor responds to changes in manifold pressure (vacuum). The ECM receives this information as a signal voltage that will vary from about 1/1.5 volts at idle (high vacuum) to 4/4.5 volts at wide open throttle (low vacuum). If the MAP sensor fails the ECM will substitute a fixed value and use the TPS to control fuel delivery.


NOTE: Because of all the possible color code combinations used on electrical wiring diagrams, always refer to ECM CONNECTOR IDENTIFICATION under ELECTRICAL AND ELECTRONIC WIRING DIAGRAMS for correct color code identification of circuit.

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. Code 34 will set if:

^ MAP signal voltage to low.
^ Engine speed is below 1200 rpm and TPS is over 20%.

2. Jumpering harness terminals "B" to "C", 5 volts to signal, will determine if the sensor is at fault or if there is an ECM or wiring problem.

3. The scan tool may not display battery voltage. The important thing is that the ECM recognizes the voltage as more than 4 volts, indicating that the ECM and circuit 432 are OK.




DIAGNOSTIC AIDS:

^ With the ignition "ON" and the engine stopped, the manifold pressure is equal to atmospheric pressure and the signal voltage will be high. This information is used by the ECM as an indication of vehicle altitude an is referred to as BARO. Comparison of this reading with a known good vehicle with the same sensor is a good way to check the accuracy of a suspected sensor. Reading should be the same +/- 0.4 volts.

^ A Code 34 will result if circuit 474 or 432 is open, or shorted to ground.

^ If circuit 416 is shorted to ground, there may also be a stored Code 22. If code 34 is intermittent, Refer to TESTING PROCEDURES/DIAGNOSIS BY SYMPTOM/INTERMITTENTS.