DTC 34

DIAGNOSTIC CHART





WIRING DIAGRAM

INSPECTION PROCEDURE

Circuit Description:
The Manifold Absolute Pressure (MAP) sensor responds to changes in manifold pressure (vacuum). The Engine Control Module (ECM) receives this information as a signal voltage that will vary from about 1-1.5 volts at idle to 4-4.5 volts at Wide Open Throttle (WOT).
If the MAP sensor fails, the ECM will substitute a fixed MAP value and use the Throttle Position (TP) Sensor to control fuel delivery.

Test Description:
Number(s) below refer to circled number(s) on the diagnostic chart.
1. DTC 34 will set when:
- Signal is too low (kPa less than 14) and engine running less than 1200 rpm. OR
- Engine running greater than 1200 rpm.
- Throttle position greater than 15% (over 1.5 volts).
2. If the ECM recognizes the high MAP signal, the ECM and wiring are OK.
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 C11 are OK.

Diagnostic Aids:
An intermittent open in CKTs C11 or C14 will result in a DTC 34.
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 Barometric Pressure (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.
Also CHART C-1D can be used the test the MAP sensor.
Refer to "Intermittents" in "Symptoms".