Powertrain Controls - ECM/PCM

DTC 33 MAP (VCM/PCM):

Circuit Description:
The Manifold Absolute Pressure (MAP) sensor responds to changes in manifold pressure (vacuum). The control module receives this information as a signal voltage that will vary from about 1-1.5 volts at closed throttle (idle) to 4-4.6 volts at Wide Open Throttle (WOT) (low vacuum).

If the MAP sensor fails, the control module will substitute a fixed MAP value and use the Throttle Position Sensor (TPS) to control fuel delivery.

Test Description:
Number(s) below refer to circled number(s) on the diagnostic chart.

1. This step will determine if DTC 33 is the result of a hard failure or an intermittent condition. A DTC 33 will set under the following conditions:
- MAP signal voltage is too high (low vacuum).
- TPS less than 3% (2% for VCM).
- These conditions exist longer than 5 seconds.
- Engine misfire or a low unstable idle may set DTC 33.

2. This step simulates conditions for a DTC 34. If the control module recognizes the change, the control module and CKT 416 and CKT 432 are OK. If CKT 455 is open, there may also be a stored DTC 23.

Diagnostic Aids:
With the ignition "ON" and the engine stopped, the manifold pressure is equal to atmospheric pressure and the signal voltage will be high. This information is used by the control module as an indication of vehicle altitude. Comparison of this reading with a known good vehicle with the same sensor is a good way to check accuracy of a "suspect" sensor. Readings should be the same +/- 0.4 volt.

A DTC 33 will result if CKT 455 is open or if CKT 432 is shorted to voltage or to CKT 474.

If DTC 33 is intermittent. - Intermittent Malfunctions
- Check all connections.
- Disconnect sensor from bracket and twist sensor connections. Output changes greater than 0.1 volt indicates a bad connector or connection. If OK, replace sensor.

NOTE: Make sure electrical connector remains securely fastened.

- for further diagnosis, see Manifold Absolute Pressure Output Check.

MAP Sensor Circuit (PCM):

Automatic Transmission (PCM) Circuit

MAP Circuit (VCM):

Manual Transmission (VCM) Circuit