DTC 34
Code 34 Chart:
Wiring Diagram For MAP Sensor:
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 1.0-1.5 volts at idle to 4.5-4.8 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: The numbers below refer to circled numbers on the diagnostic chart.
1. This step determines if Code 34 is the result of a hard failure or an intermittent condition. A Code 34 will set when:
a. MAP signal voltage is too low.
b. Engine speed idle less than 1200 rpm and throttle angle is greater than 20%.
2. Jumpering harness terminals "B" to "C" (5.0 volts to signal circuit) 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 5.0 volts, but the ECM recognizes the voltage as more than 4.0 volts, indicating that the ECM and circuit 432 are OK.
DIAGNOSTIC AIDS:
1. With the ignition "ON" and the engine not running, the manifold pressure is equal to atmospheric pressure and the signal voltage will be high. This information is used by the ECM as an indication of vehicle altitude and is referred to as BARO. A comparison of this BARO reading, with a known good vehicle with the same sensor, is a good way to check the accuracy of the problem sensor. BARO readings should be similar within +/- 0.4 volts. CHART C-1D can be used to test the MAP sensor.
2. A Code 34 will result if circuits 416 or 432 are open, or shorted to ground.
3. If circuit 416 is open or shorted to ground, there may be a Code 22 stored.
4. If a Code 34 is intermittent, see DIAGNOSIS BY SYMPTOM.
5. Check all connections. Disconnect the sensor from the bracket and twist sensor (by hand only) to check for intermittent connections. Output changes greater than 0.1 volt indicates a faulty connector or connection. If OK, replace sensor.