Diagnostic Aids

NOTE: If this code IS NOT displayed during the third pass of diagnostic codes, it is an intermittent failure and cannot be diagnosed using this procedure. For an intermittent code, refer to NOTE ON INTERMITTENTS.

Trouble Code 34 indicates that the Manifold Absolute Pressure sensor (MAP) signal and the Barometric Pressure sensor (BARO) signal have closed to the same value when the engine is running. This condition can be observed in engine data display as MAP (parameter .0.2) and BARO (parameter .0.3) readings within 6 kPa of each other with the engine running at idle. When the ignition is on and the engine is not cranking or running, both sensors should read the same voltage value because they are reading atmospheric (barometric) pressure. As the engine starts to turn over, the MAP sensor should read manifold pressure. Possible causes of Code 34 are:

A. A MAP hose leak or blockage.
B. Defective wires, terminals, etc.
C. An ECM not processing the signals properly.

After verifying the failure condition, the MAP hose should be inspected for leaks or blockages and repaired as necessary.
If the MAP hose is OK, create a low sensor signal by disconnecting the MAP sensor. If the "MAP" reading is 17 kPa or greater, then either the wiring harness or the ECM is shorted to voltage. If no defect is found in circuit 432 then the short to voltage is either in the ECM connector or in the ECM itself
If the "MAP" reading is 14 to 16 kPa, circuit 476-Y must be checked for an open. If the voltage between circuits 474 and 476-Y is 0 volts, circuit 476-Y is open. If the voltage is 5 volts, the ECM and wiring are OK. The fault must be improper mating of sensor terminals or a faulty MAP sensor.