DTC 33

DTC 33 Circuit Diagram:

DTC 33 Diagnostic Chart Hi Voltage/Lo Vacuum Indicated From 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 0.53-0.61 volts, at closed throttle idle, to 2.18-4.28 volts at wide open throttle (low vacuum). If the MAP sensor fails, the ECM will substitute a fixed MAP value and use the TPS 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 an intermittent condition. Code 33 will set if:

^ MAP signal indicates greater than 90 kPa (low vacuum).
^ No Code 21, 22 or 31 is set.
^ TPS less than 1%.
^ These conditions are present longer than 15 seconds.

2. This step simulates conditions for a Code 34 (signal voltage low-high vacuum). If the ECM recognizes the change, the ECM, GRY wire and GRY/RED wire are OK. If BLU/ORN wire is open, there may also, be a stored Code 22.

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 ECM as an indication of vehicles altitude and is referred to as BARO. Comparison of this BARO reading with a known good vehicles with the same sensor is a good way to check accuracy of a suspect sensor. Readings should be the same ± 0.4 volts. A Code 33 will result if GRY wire is open, or if GRY/RED wire is shorted to voltage or to BLU/ORN. If Code 33 is intermittent,
Intermittant Check Procedure