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.

The ECM supplies a 5 volt signal to pin C (circuit 474) of the Manifold Absolute Pressure (MAP) Sensor and supplies a ground path to pin A (circuit 476-Y). The MAP signal from pin B (circuit 432) is a variable voltage which is dependent on the manifold pressure.

Trouble Code 31 indicates that the voltage signal from the MAP sensor is too high. This situation can be observed in engine data display as a "MAP" reading (parameter .0.2) of 106 to 108 kPa. Possible causes of this condition are:

A. Defective MAP sensor.
B. Defective wiring, terminals, etc.
C. An ECM which is unable to process signals properly.

If the opposite condition (low MAP signal) can be created, then the self-diagnostics can be used to detect this failure by displaying engine data parameter .0.2. With the opposite condition created, parameter .0.2 should display a "MAP" reading of 14 to 16 kPa. To create a low sensor signal, disconnect the MAP sensor connector. If the "MAP" reading is 14 to 16 kPa, then the problem must be a faulty MAP sensor. If the "MAP" reading is 17 kPa or greater, then there is a short to voltage in the wiring or the ECM.