Wednesday, June 8, 2011

Jeep Cherokee Limited Will not start, cant read codes

VEHICLE: 1999 Jeep Cherokee Limited 4.0L, L6, MFI, OHV, VIN S, Eng Desg -

MILEAGE: 100000

Customer Concern: No start, no communication with the scan tool.


1. Test powers and grounds at the Powertrain Control Module (PCM) on the C1 connector. Pins 2 and 22 are power, then check pins 31 and 32 for ground.

2. Then test the 5 volt power supplies at pin 17 of the C140 connector and pin 31 of the C141 connector, for shorts to ground. Sensors on the circuit are the Cam Angle Sensor (CMP), Crank Angle Sensor (CKP), Throttle Position Sensor (TPS), Manifold Absolute Pressure Sensor (MAP) and Vehicle Speed Sensor (VSS).

3. Unplug the sensors on the 5 volt power supply, one at a time, while monitoring the 5 volt supply.

4. When the shorted sensor is unplugged, the PCM will wake up and scan tool communication will return after the key is cycled.

Potential Causes:

Powertrain Control Module (PCM)

Camshaft Position Sensor (CMP)

Crankshaft Position Sensor (CKP)

Manifold Absolute Pressure (MAP) Sensor

Throttle Position Sensor (TPS)

Vehicle Speed Sensor (VSS)


Confirmed Fix: Replaced Crankshaft Position (CKP) Sensor

Tech Tips: The wiring harness could also be shorted to ground on one of the 5 volt power supply wires. Cut the wires at the PCM on pins C140-17 and C141-31, then check for the 5 volts on the PCM of the connector or check for any continuity to ground with the sensors unplugged at the PCM connector on C140-17 and C141-31 to check the wiring harness.
Jeep Cherokee Limited 4.0L will not start

No comments:

Post a Comment