Diagnostic Test

WARNING: This page is about a different car, the 2005 Jeep Grand Cherokee. However, it is still accessible from the selected car via links, so may be relevant.

1) ACTIVE DTC
NOTE: Check the vehicle repair history. If the 1/2 O2 has been replaced make sure that the O2 sensor was properly installed and meets OEM specification.

NOTE: Check for contaminants that may have damaged the O2 Sensor: contaminated fuel, unapproved silicone, oil and coolant.

Ignition on, engine not running.

With a scan tool, read DTCs.

Is the DTC active at this time?

Yes
1. Go To step 2).
No
1. Refer to INTERMITTENT CONDITION .
2. Perform POWERTRAIN VERIFICATION TEST .
2) EXHAUST LEAK
Turn the ignition off.

WARNING: To avoid personal injury from the exhaust system being hot, allow the exhaust to cool down to a safe temperature before performing a physical inspection. Failure to follow these instructions can result in personal injury or death.

Visually and Physically inspect the exhaust system for holes, cracks and blockage in the exhaust system.

Is the exhaust system is good condition?

Yes
1. Go To step 3).
No
1. Repair or Replace as necessary.
2. Perform POWERTRAIN VERIFICATION TEST .
3) ENGINE MECHANICAL
Check for any of the following conditions/mechanical problems

AIR INDUCTION SYSTEM - must be free from leaks.

ENGINE VACUUM - must be at least 13 inches in neutral

ENGINE VALVE TIMING - must be within specifications

ENGINE COMPRESSION - must be within specifications

ENGINE EXHAUST SYSTEM - must be free of any restrictions or leaks

ENGINE PCV SYSTEM - must flow freely

TORQUE CONVERTER STALL SPEED - must be within specifications

POWER BRAKE BOOSTER - no internal vacuum leaks

FUEL - must be free of contamination

FUEL INJECTOR - plugged or restricted injector; control wire not connected to correct injector

Are there any engine mechanical problems?

Yes
1. Repair as necessary.
2. Perform POWERTRAIN VERIFICATION TEST .
No
1. Go To step 4).
4) O2 SENSOR

Fig 1: Checking O2 Sensor
Courtesy of DAIMLERCHRYSLER CORP.

Ignition on, engine not running.

Disconnect the 1/2 O2 Sensor harness connector.

With the scan tool, monitor the 1/2 O2 Sensor voltage.

The O2 Sensor voltage should read 5.0 volts on the scan tool with the connector disconnected.

Using a jumper wire, jump the (K141) O2 Sensor 1/2 Signal circuit to the (K904) O2 Return Downstream circuit in the O2 Sensor harness connector.

NOTE: The voltage should drop from 5.0 volts to 2.5 volts with the jumper wire in place.

Did the O2 Sensor volts change from 5.0 volts to 2.5 volts?

Yes
1. Replace the O2 Sensor
2. Perform POWERTRAIN VERIFICATION TEST .
No
1. Go To step 5).
5) (K141) O2 SENSOR 1/2 SIGNAL CIRCUIT

Fig 2: Checking O2 Sensor Signal Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Fig 3: Checking O2 Sensor Signal Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Remove the jump wire.

Ignition on, engine not running.

With the scan tool, monitor the 1/2 O2 Sensor voltage.

Is the voltage above 4.8 volts?

Yes
1. Go To step 6).
No
1. Check the (K141) O2 Sensor 1/2 Signal circuit for an open or short to voltage. Inspect the O2 Sensor connector and the PCM harness connector. If OK, replace and program the Powertrain Control Module per Service Information.
2. Perform POWERTRAIN VERIFICATION TEST .
6) (K299) O2 SENSOR 1/2 HEATER CONTROL CIRCUIT OPEN

Fig 4: Checking O2 Sensor Heater Control Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition off.

Disconnect the C3 PCM harness connector.

Measure the resistance of the (K299) O2 Sensor 1/2 Heater Control circuit from the O2 Sensor harness connector to the appropriate terminal of special tool #8815.

Is the resistance below 5.0 ohms?

Yes
1. Go To step 7).
No
1. Repair the open in the (K299) O2 Sensor 1/2 Heater Control circuit.
2. Perform POWERTRAIN VERIFICATION TEST .
7) (K904) O2 RETURN DOWNSTREAM CIRCUIT

Fig 5: Checking O2 Sensor Return Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Fig 6: Checking O2 Sensor Return Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Measure the voltage on the (K904) O2 Return Downstream circuit in the O2 Sensor harness connector.

Is the voltage at 2.5 volts?

Yes
1. Check the fuel system for contaminants.
2. Perform POWERTRAIN VERIFICATION TEST .
No
1. Check the (K904) O2 Return Downstream circuit for a short to ground, open, or short to voltage. Inspect the O2 Sensor connector and the PCM harness connector. If OK, replace and program the Powertrain Control Module per Service Information.
2. Perform POWERTRAIN VERIFICATION TEST .