Powertrain Controls - ECM/PCM

Code 34 Chart:

Manifold Absolute Pressure Sensor Wiring Diagram:

CIRCUIT DESCRIPTION:

The Manifold Absolute Pressure (MAP) Sensor responds to changes in manifold pressure (vacuum). The Electronic Control Module (ECM) receives this information as a signal voltage that will vary from about 1 to 1.5 volt at idle (high vacuum) to 4-4.5 volts at wide open throttle (low vacuum).

NOTE: Because of all the possible color code combinations used on electrical wiring diagrams, always refer to SCHEMATIC DIAGRAMS/ELECTRICAL AND ELECTRONIC WIRING DIAGRAMS/ECM CONNECTOR IDENTIFICATION 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:

- Engine speed is less than 1200 rpm.
- Manifold pressure less than 13 kPa
- Conditions met for 1 second
OR
- Engine speed is greater than 1200 rpm.
- Manifold pressure less than 13 kPa
- Throttle angle greater than 20%
- 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 for an open in CKT 432. If the test lite is bright, CKT 432 is probably shorted to ground. If scan reads 4 + volts, CKT 474 can be checked @ terminal "C", it should be 5 volts.

DIAGNOSTIC AIDS:


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

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

Refer to TESTING PROCEDURES/DIAGNOSIS BY SYMPTOM/INTERMITTENTS.