With PFI

Code 34 - Manifold Absolute Pressure (MAP) Sensor:

Wiring Diagram for Manifold Absolute Pressure (MAP) Sensor:

CODE 34 - MANIFOLD ABSOLUTE PRESSURE SENSOR CIRCUIT (MAP) SIGNAL VOLTAGE LOW - HIGH VACUUM

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 MAP 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. This step will determine 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 below 14 kPa

^ Engine speed below 1200 rpm and/or TPS greater than 20%

2. Jumpering harness terminals "B" to "C".5 volts 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:


With the ignition "ON" and the engine stopped, 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. Comparison of this BARO reading with a known good vehicle with the same sensor is a good way to check accuracy of a "suspect" sensor. Reading should be the same +/- .4 volt.

A Code 34 will result if CKTs 474 or 432 are open, or shorted to ground.

If CKT 416 is shorted to ground, there may also be a stored Code 22.

If Code 34 is intermittent, refer to Diagnosis By Symptoms - No Trouble Codes Stored.