Diagnostic Aids

If a shared 5-volt reference circuit is shorted to ground or shorted to a voltage, the other 5-volt reference circuits may be affected.
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 test the accuracy of a suspect sensor.
For an intermittent condition, refer to Intermittent Conditions .

Step	Action	Values	Yes	No
Schematic Reference: Engine Controls Schematics (European Emissions) or Engine Controls Schematics (Non European Emissions) Connector End View Reference: Engine Controls Connector End Views
1	Did you perform the Diagnostic System Check - Engine Controls?	-	Go to Step 2	Go to Diagnostic System Check - Engine Controls
2	Start the engine. Allow the engine to reach the normal operating temperature. Observe the DTC Information with a scan tool. Did the DTC fail this ignition?	-	Go to Step 4	Go to Step 3
3	Observe the Freeze Frame/Failure Records for this DTC. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data. Did the DTC fail this ignition cycle?	-	Go to Step 4	Go to Diagnostic Aids
4	Turn OFF the ignition. Disconnect the manifold absolute pressure (MAP) sensor electrical connector. Turn ON the ignition, with the engine OFF. Measure the voltage from the 5-volt reference circuit of the MAP sensor to a good ground. Is the voltage within the specified range?	4.8-5.2 V	Go to Step 5	Go to Step 6
5	Connect a 3-amp fused jumper wire between the 5-volt reference circuit and the signal circuit of the MAP sensor. Observe the MAP sensor parameter with a scan tool. Is the pressure more than the specified value?	102 kPa	Go to Step 8	Go to Step 7
6	IMPORTANT: The 5-volt reference circuits are internally and externally connected at the controller. Other sensors that share the 5-volt reference circuit may also have DTCs set. Disconnecting a sensor on the shared 5-volt reference circuit may isolate a shorted sensor. Review the electrical schematic and diagnose the shared circuits and sensors. Test the 5-volt reference circuit of the MAP sensor for the following conditions: An open A short to ground High resistance Refer to Circuit Testing and Wiring Repairs in Wiring Systems.Did you find and correct the condition?	-	Go to Step 12	Go to Step 9
7	Test the signal circuit of the MAP sensor for the following conditions: An open A short to ground High resistance Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 12	Go to Step 9
8	Test for an intermittent and for a poor connection at the MAP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 12	Go to Step 10
9	Test for an intermittent and for a poor connection at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 12	Go to Step 11
10	Replace the MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement . Did you complete the replacement?	-	Go to Step 12	-
11	Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement?	-	Go to Step 12	-
12	Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition?	-	Go to Step 2	Go to Step 13
13	Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed?	-	Go to Diagnostic Trouble Code (DTC) List	System OK