DTC 31

Fig. 24 Manifold absolute pressure sensor & barometric pressure sensor wiring circuit. 1984:

Fig. 25 Manifold absolute pressure sensor & barometric pressure sensor wiring circuit. 1985:

If this code is not displayed during the third pass of diagnostic codes, the problem is an intermittent failure. To help isolate the problem, manipulate related wiring while observing parameter .0.2. If failure is induced, MAP reading will jump from its normal value to a shorted reading of 106 to 108 kPa.
The ECM supplies 5 volts to circuit 474 of the manifold absolute pressure (MAP) sensor and supplies a 5 volt ground path through circuit 476Y. The MAP signal from circuit 432 is a variable voltage, dependent on manifold pressure. Code 31 indicates that the voltage signal from the MAP sensor is too high. This situation will be observed in parameter .0.2 as an MAP reading of 106 to 108 kPa. Possible causes of this condition are:
a. Defective MAP sensor.
b. Defective wiring or electrical connectors.
c. ECM unable to properly process signals.
1. Turn ignition on, enter diagnostics and display parameter .0.2.
2. Disconnect sensor electrical connector and note parameter value.
3. If value of parameter .0.2 is 14 to 16, replace MAP sensor.
4. If value of parameter .0.2 is 17 or more, inspect circuit 432 for a short to voltage and repair as necessary. If wire is satisfactory, fault is in ECM or ECM connector.