With TBI

Fig. 040 Code 34 MAP Sensor Circuit:

Fig. 041 Code 34 MAP Sensor Circuit:

CODE 34

MAP SENSOR CIRCUIT

SIGNAL VOLTAGE LOW

(HIGH VACUUM)

2.5L "A, N & P" SERIES

2.0L "J & L" SERIES

FUEL INJECTION (TBI)

Circuit Description: The Manifold Absolute Pressure Sensor (MAP) 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 closed throttle idle, to 4 - 4.5 volts at wide open throttle.
If the MAP sensor fails, the ECM will substitute a fixed MAP value and use the Throttle Position Sensor (TPS) to control fuel delivery.

Test Description: Numbers below refer to circled numbers on Diagnostic Charts.

1. This step determines if Code 34 is the result of a hard failure or an intermittent condition.
A Code 34 will set when:
MAP signal voltage is too low.
The ignition in "ON"
2. Jumpering harness terminals "B" to "C", 5 volt to signal, will determine if the sensor is at fault, or if there is a problem with the ECM or wiring.
3. The "Scan" tool may not display 12 volts. The important thing is that the ECM recognizes the voltage as more than 4 volts, indicating that the ECM and CKT 432 are OK.

Diagnostic Aids:

The ignition "ON", engine stopped; voltage guide in the flow chart may be used to determine the accuracy of the MAP sensor. This voltage reading is used by the ECM as a Barometric pressure reading.
A Code 34 will result if CKTs 416 or 432 are open or shorted to ground.
If Code 34 is intermittent, refer to DIAGNOSIS BY SYMPTOM.