DTC 33

Code 33 Chart:

Wiring Diagram For MAP Sensor:

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 1.0-1.5 volts at idle, to 4.0-4.5 volts at wide open throttle. If the MAP sensor fails, the ECM will substitute a fixed MAP value and use the Throttle Position Sensor (TPS) to control fuel delivery.

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

1. This step will determine if a Code 33 is the result of a hard failure or an intermittent condition. A Code 33 will set if:
a. The engine is running.
b. MAP signal indicates greater than 80.0 kPa (low vacuum).
c. TPS less than 12%
d. These conditions are present 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 416 and 432 are OK. If circuit 469 is open, there may also be a Code 23 stored.

DIAGNOSTIC AIDS:

1. With the ignition "ON" and the engine not running, the manifold pressure is equal to atmospheric pressure and the signal voltage will be high. This information is used by the ECM as an indication of vehicle altitude and is referred to as BARO. A comparison of this BARO reading, with a known good vehicle with the same sensor, is a good way to check the accuracy of the problem sensor. BARO readings should be similar within +/- 0.4 volts.
2. A Code 33 will result if circuit 469 is open, or if circuit 432 is shorted to voltage or to circuit 416.
3. If a Code 33 is intermittent, see DIAGNOSIS BY SYMPTOM.