DTC 34

Fig. 040 Code 34 MAP Sensor Circuit:

Fig. 041 Code 34 MAP Sensor Circuit:

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.