Hey Mike.
The voltage really need's to be able to vary slightly that is the job of the sensor ..so keeping it at a constant voltage is not really an option !! My manual states the following voltage's I would check this first before buying new !!
CODE 31 - MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR CIRCUIT
CAUTION:If ECM replacement is instructed in following testing, always ensure ECM harness connector and ground circuit are okay. If either are suspect, repair and repeat testing to confirm ECM malfunction.
Circuit Description
MAP sensor detects manifold pressure as a voltage that is supplied to the ECM to determine basic injection duration and advance angle. Code is set when ECM detects a open or short in MAP circuit. ECM will operate in fail-safe mode if Code 31 is set. Possible causes are:
MAP open or short circuit.
MAP sensor malfunction.
ECM malfunction.
Diagnosis & Repair
Access ECM behind glove box. Ensure ignition is on. Using DVOM, backprobe ECM harness connector. Measure voltage between terminals VC and E2. see Fig. 6 (A/T & M/T). If voltage is 4.5-5.5 volts, go to next step. If voltage is NOT 4.5-5.5 volts, replace ECM and retest.
Measure voltage between ECM terminals PIM and E2. If voltage is 3.3-3.9 volts, go to next step. If voltage is NOT 3.3-3.9 volts, replace ECM and retest.
Inspect circuits between MAP and ECM for open or short. Repair as needed. If circuits are okay, replace MAP sensor.
Friday, June 5th, 2009 AT 5:07 AM