DTC 34

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 to 1.5 volts at idle to 4-4.5 volts at wide open throttle.

If the MAP sensor fails the ECM will substitute a fixed value and use the throttle position sensor (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 when:

^ When engine is less than 600 rpm.
^ Manifold pressure reading less than 13 kPa, conditions met for 1 second or
^ Engine is greater than 600 rpm.
^ Throttle angle over 20%.
^ Manifold pressure less than 13 kpa conditions met for 1 second.

2. This tests to see if the sensor is at fault for the low voltage or if there is a ECM or wiring problem.

3. This simulates a high signal voltage to check of an open in CKT 432. if the test light is bright during this test, CKT 432 is probable shorted to ground. If "Scan" reads over 4 volts at this test CKT 474 can be checked by measuring the voltage at terminal "C". (should be 5 volts)


DIAGNOSTIC AIDS:


An intermittent open in circuit 432 or 474 will result in a Code 34.

Ignition "ON" engine "OFF" voltages should be within the table on the chart above. Also, CHART C-1D can be used to test the MAP sensor.

Refer to TESTING PROCEDURES/DIAGNOSIS BY SYMPTOM/INTERMITTENTS.