Diagnostic Procedure
WARNING: This page is about a different car, the 2005 Jeep Liberty. However, it is still accessible from the selected car via links, so may be relevant.
NO RESPONSE FROM PCM WITH NO START CONDITION DIAGNOSTIC TEST REFERENCE
| TEST | ACTION | APPLICABILITY |
|---|---|---|
| 1 |
NOTE:
The DRBIII® and cable must be operating properly for the results of this test to be valid.
NOTE:
Ensure the ignition switch was on while trying to communicate with the PCM. Turn the ignition off.Disconnect the PCM harness connectors.Using a 12-volt test light connected to ground, probe the PCM Fused B+ circuit in the PCM harness connector.Does the test light illuminate brightly?Yes --> Go To 2No --> Repair the open or short to ground in the Fused B+ circuit. Inspect and replace fuses as necessary.Perform POWERTRAIN VERIFICATION TEST VER - 1 . |
All |
| 2 | Ignition on, engine not running. Using a 12-volt test light connected to ground, probe the PCM Fused Ignition Switch Output circuit in the PCM harness connector. Does the test light illuminate brightly? Yes --> Go To 3 No --> Repair the Ignition Switch Output circuits. Inspect and replace fuses as necessary. Perform POWERTRAIN VERIFICATION TEST VER - 1 . |
All |
| 3 | Turn the ignition off. Using a 12-volt test light connected to battery voltage, probe the (Z81), (Z82) PCM ground circuits in the PCM harness connector. Does the test light illuminate brightly? Yes --> Go To 4 No --> Repair the (Z81), (Z82) PCM ground circuits. Perform POWERTRAIN VERIFICATION TEST VER - 1 . |
All |
| 4 | Connect the PCM harness connectors. Disconnect the TP Sensor harness connector. Ignition on, engine not running. Measure the voltage on the (F855) 5-volt Supply circuit. Is the voltage between 4.5 and 5.2 volts? Yes --> Go To 5 No --> Go To 6 |
All |
| 5 | Turn the ignition off. Disconnect the MAP Sensor harness connector.
NOTE:
Connect the TP Sensor harness connector. Ignition on, engine not running. Measure the voltage on the MAP Sensor 5 Volt Supply circuit. Is the voltage between 4.5 and 5.2 volts? Yes --> If communication is available with a PCM on a like vehicle, replace and program the Powertrain Control Module per Service Information. Perform POWERTRAIN VERIFICATION TEST VER - 1 . No --> Replace the Throttle Position Sensor. Perform POWERTRAIN VERIFICATION TEST VER - 1 . |
All |
| 6 | Turn the ignition off. Disconnect the TP Sensor harness connector. Ignition on, engine not running. Measure the voltage on the (F855) 5-volt Supply circuit. Disconnect all the sensors that use (F855) 5-volt Supply circuit. Did the voltage return to 4.5 to 5.2 volts when disconnecting any of the sensors. Yes --> Replace the sensor that is pulling down the 5-volt supply. Perform POWERTRAIN VERIFICATION TEST VER - 1 . No --> Go To 7 |
All |
| 7 | Turn the ignition off. Disconnect PCM harness connectors. Measure the resistance between ground and the (F855) 5-volt Supply circuit with all the Sensor harness connectors disconnected. Is the resistance below 100 ohms? Yes --> Repair the short to ground in the (F855) 5-volt Supply circuit. Perform POWERTRAIN VERIFICATION TEST VER - 1 . No --> Go To 8 |
All |
| 8 | Disconnect all sensors that use the (F856) 5-volt Supply. Measure the resistance between ground and the (F856) 5-volt Supply circuit in the PCM harness connector. Is the resistance below 100 ohms? Yes --> Repair the short to ground in the (F856) 5-volt Supply circuit. Perform POWERTRAIN VERIFICATION TEST VER - 1 . No --> Go To 9 |
All |
| 9 |
NOTE:
Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary. Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.If there is no possible causes remaining, view repair.RepairReplace and program the Powertrain Control Module per Service Information.Perform POWERTRAIN VERIFICATION TEST VER - 1 . |
All |