DTC 33

DIAGNOSTIC CHART





WIRING DIAGRAM

INSPECTION PROCEDURE

Circuit Description:
The MAP sensor responds to changes in manifold pressure (vacuum). The Engine Control Module (ECM) receives this information as a signal voltage that will vary from about 1-1.5 volts at idle to 4.5-4.8 volts at Wide Open Throttle (WOT).
A "Scan" displays manifold pressure in volts. Low pressure (high vacuum) reads a low voltage while a high pressure (low vacuum) reads a high voltage.
If the MAP sensor fails, the ECM will substitute a fixed MAP value and use the Throttle Position (TP) Sensor to control fuel delivery.

Test Description:
Number(s) below refer to circled number(s) on the diagnostic chart.
1. DTC 33 will set when:
- Signal is too high, (kPa greater than 82 kPa), for a time greater than 5 seconds.
- TP Sensor less than 4%.
- Vehicle speed is above 2 mph.
Engine misfire or a low unstable idle may set DTC 33. Disconnect MAP sensor and system will go into backup mode. If the misfire or idle condition remains, see "Symptoms".
2. If the ECM recognizes the low MAP signal, the ECM and wiring are OK.

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 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 ±.4 volt.
If idle is rough or unstable refer to "Symptoms" for items which can cause an unstable idle.
An open in CKT All or the connection will result in a DTC 33.
- Check all connections.

NOTE:
- 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 connection. If OK, replace sensor.
- Refer to "Intermittents" in "Symptoms".