Diagnostic Instructions

DTC Descriptors

DTC 033: Manifold Absolute Pressure (MAP) Sensor Circuit High Voltage

DTC 034: Manifold Absolute Pressure (MAP) Sensor Circuit Low Voltage

Circuit/System Description

The manifold absolute pressure (MAP) sensor responds to changes in the manifold vacuum. The electronic control module (ECM) receives this information as a signal voltage that will vary from about 1-1.5 volts at closed throttle, idle, to 4.5-5 volts at wide open throttle.

Conditions for Setting the DTC

DTC 033

DTC 034

Diagnostic Aids

If a shared 5-volt reference circuit is shorted to ground or shorted to a voltage, other 5-volt reference circuits may be affected.

Reference Information

Schematic Reference

Engine Controls Schematics

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Special Tools

J 23738-A Vacuum Pump

Circuit/System Verification

Engine running, observe the scan tool MAP Sensor parameter. The reading should be between 32-42 kPa.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the MAP sensor.
2. Ignition OFF, test for less than 5 ohms between the low reference circuit terminal 1 and ground.

⇒	If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

Important: The 5-volt reference circuits are internally and externally connected at the ECM. Other component DTCs may be set. If other DTCs are set, review the electrical schematic and diagnose the applicable circuits and components.

3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 3 and ground.

⇒	If less than the specified range, test the 5-volt reference circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the ECM.

⇒	If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.

4. Verify the scan tool MAP sensor parameter is less than 12 kPa.

⇒	If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.

5. Install a 3A fused jumper wire between the signal circuit terminal 2 and the 5-volt reference circuit terminal 3. Verify the scan tool MAP sensor parameter is greater than 102 kPa.

⇒	If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

6. If all circuits test normal, test or replace the MAP sensor.

Component Testing

1. Ignition OFF, perform one of the following applicable procedures:

•	Disconnect the vacuum supply hose from the MAP sensor.

•	Remove the MAP sensor from the intake manifold.

2. Ignition ON, observe and record the scan tool MAP sensor pressure data parameter. This is the first MAP sensor reading.
3. With the J 23738-A apply 5 in Hg (17 kPa) of vacuum to the MAP sensor. Observe and record the scan tool MAP sensor pressure data parameter. This is the second MAP sensor reading.
4. Subtract the second MAP sensor reading from the first MAP sensor reading. Verify that the vacuum decrease is within 1 in Hg (4 kPa) of the applied vacuum.

⇒	If not within the specified range, replace the MAP sensor.

5. With the J 23738-A apply 10 in Hg (34 kPa) of vacuum to the MAP sensor. Observe and record the scan tool MAP sensor pressure data parameter. This is the third MAP sensor reading.
6. Subtract the third MAP sensor reading from the first MAP sensor reading. Verify that the vacuum decrease is within 1 in Hg (4 kPa) of the applied vacuum.

⇒	If not with in the specified range, replace the MAP sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.