DTC 33

Code 33 Chart:

Code 33 Wiring Diagram:

CIRCUIT DESCRIPTION:


The manifold absolute pressure (MAP) sensor responds to changes in manifold pressure (vacuum). The ECM receives this information as a signal voltage that will vary from about 1 to 1.5 volts at idle, when manifold pressure is low (high vacuum), to 4 - 4.5 volts at wide open throttle (low vacuum or high pressure).

If the MAP sensor fails, the ECM will substitute a fixed MAP value and use the throttle position sensor (TPS) and other sensors to control fuel delivery.


TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. This step will determine if Code 33 is the result of a hard failure or intermittent condition.

^ MAP signal voltage to high (low vacuum).
^ TPS less than 2%.
^ The above conditions are met for a time longer than 5 seconds.

2. This step simulates conditions for a Code 34. If the ECM recognizes the change, the ECM and circuits 474 and 432 are ok. If circuit 452 is open, there may also be a Code 23 stored.




DIAGNOSTIC AIDS:

With the ignition "ON" and the engine stopped, the manifold pressure is equal to atmosphereic pressure and the signal voltage will be high. This information is used by the ECM as an indication of vehicle altitude an is refered to as BARO. Comparsion of this reading with a known good vehicle with the same sensor is a good way to check the accuracy of a suspected sensor. Reading sould be the same +/- 0.4 volts. A Code 33 will result if circuit 452 is open, or if circuit 432 is shorted to voltage or to circuit 474. If code 33 is intermittent, Refer to TESTING PROCEDURES/DIAGNOSIS BY SYMPTOM/INTERMITTENTS.