DTC 34

Code 34 - MAP Sensor Circuit Signal Voltage Low (High Vacuum):

Wiring Diagram For Code 34 - MAP Sensor Circuit Signal Voltage Low (High Vacuum):

CODE 34 - MANIFOLD ABSOLUTE PRESSURE SENSOR CIRCUIT

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.


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 lest CKT 416 can be checked by measuring the voltage at terminal "C". (should be 5 volts)


DIAGNOSTIC AIDS:

An intermittent open in CKTs 416 will result in a Code 34.

DIAGNOSIS BY SYMPTOM - NO TROUBLE CODES STORED.

The "Altitude to Voltage" scale above may be used to test the MAP sensor at a specific altitude level to evaluate the possibility of a "slewed" (mis-scaled) sensor. A "slewed" sensor could result in poor driveability complaints.