Powertrain Controls - ECM/PCM

DTC 33 Map Circuit:

MAP Sensor Wiring Schematic:

CIRCUIT DESCRIPTION
The Manifold Absolute Pressure (MAP) sensor responds to changes in the intake manifold pressure. MAP is the inverse of vacuum, so as MAP increases such as during WOT, vacuum decreases.

The MAP sensor should indicate approximately 1-2 volts at idle, and between 4 and 5 volts at Wide Open Throttle (WOT). MAP is one of the most important inputs for calculating fuel delivery.

DTC 33 Will Set When: No current DTC 21 or 22 is present, MAP is greater than 84 kPa (A/C "OFF") 87 kPa (A/C "ON"), throttle angle is between 3% and 30% and held steady. All conditions met for 4 seconds.

Action Taken (PCM will default to): A default table of MAP values will be used by the PCM to calculate air flow. The MIL will become illuminated and MAP values on the Tech 1 (or equivalent) will become maximum (5 volts).

DTC 33 Will Clear When: A current DTC 33 will clear when the MAP value falls below the calibrated high MAP threshold. A History DTC 33 will clear after 50 consecutive key cycles without a current DTC 33 being stored.

TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.

1. Engine misfire or an unstable idle may set DTC 33.
2. With the MAP sensor disconnected, the PCM should see a low voltage if the PCM and wiring are OK.


DIAGNOSTIC AIDS:

^ If idle is rough or unstable, refer to "Symptoms". Testing and Inspection
^ An open in CKT 469 or the connection will result in a DTC 33.
^ With the ignition "ON" and engine stopped, the manifold pressure is equal to atmospheric pressure and the signal voltage will be high. This information is used by the PCM 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 volts.
^ Check all connections. Make sure electrical connector remains securely fastened.
^ Disconnect sensor from bracket and twist sensor by hand (only) to check for intermittent connections. Output changes greater than .1 volt indicates a bad connector or connections. If OK, replace sensor.
^ Refer to CHART C-1D, MAP sensor voltage output check for further diagnosis. Chart C-1D Manifold Absolute Pressure (MAP) Output Check
^ Refer to in "Diagnosis by Symptoms". Testing and Inspection