P034

DTC PO34:

Sensor Circuit:

DESCRIPTION
This diagnostic test monitors the Manifold Absolute Pressure (MAP) signal for loss of engine vacuum under closed throttle conditions. If the difference between MAP signal and the calculated Barometric Absolute Pressure (BARO) is 11 kPa or less for 15 seconds, Code P034 sets.

TEST CONDITIONS
1. Codes P021, P022, P026, P027, P031, and P032, not set.
2. Throttle Position (TP) switch closed.
3. RPM 400 or greater.
4. TP sensor value 18 degrees or less.
5. BARO 75 kPa or greater.

FAILURE CONDITIONS
Difference between MAP and Calculated BARO 11 kPa or less for 15 seconds.

ACTION TAKEN
1. Powertrain Control Module (PCM) turns "ON" the "Service Engine Soon" Malfunction Indicator Lamp (MIL).
2. PCM uses a substitute MAP value based on engine RPM and throttle position switch status.
3. PCM disables long term fuel trim.

NOTES ON FAULT TREE
1. MAP at idle should be 30 - 50 kPa, depending on engine load. BARO should be 85 to 105 kPa, depending on altitude.

2. Check for vacuum at the fuel pressure regulator hose with a vacuum gauge. At idle, typical vacuum readings are 14 - 20 inches Hg depending on engine load.

3. Checking for MAP sensor or MAP circuit faults.

4. Checking for sensor ground open from sensor to PCM.

5. Checking for short to voltage or sensor signal CKT 432.

6. Fault is most likely at PCM connector or PCM. Before PCM is replaced, check for damaged pins or poor connection.

NOTES ON INTERMITTENTS
Code P034 is usually set by a vacuum supply problem to the MAP sensor. Check for proper vacuum routing. Apply vacuum to the MAP sensor and look for leaks in MAP sensor. Manipulate affected wiring and connectors while observing PCM data PD02. Apply and release vacuum to the MAP hose using a vacuum source. If the PCM data display jumps high with vacuum applied, the failure has been induced and the cause of the intermittent can be repaired. If wiring and connectors check out OK, substitute a known good MAP sensor and retest.