Diagnostic Test

WARNING: This page is about a different car, the 2007 Chrysler PT Cruiser. 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 Sensor 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 2).
No
1. Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Refer to INTERMITTENT CONDITION .
2. Perform POWERTRAIN VERIFICATION TEST .
2) CHECKING THE EXHAUST SYSTEM FOR LEAKS
Perform the diagnostic procedure for *CHECKING THE EXHAUST SYSTEM FOR LEAKS.

Were any problems found?

Yes
1. Repair as necessary.
2. Perform POWERTRAIN VERIFICATION TEST .
No
1. Go to 3).
3) ENGINE MECHANICAL PROBLEM
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 4).
4) O2 SENSOR

Fig 1: Checking O2 Sensor Operation
Courtesy of CHRYSLER LLC

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 (K902) O2 Downstream Return 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 5).
5) (K141) O2 SENSOR 1/2 SIGNAL CIRCUIT
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 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

Fig 2: Measuring Resistance Between Ground & O2 Sensor 1/2 Heater Control Circuit
Courtesy of CHRYSLER LLC

Turn the ignition off.

Measure the resistance between ground and the (K299) O2 Sensor 1/2 Heater Control circuit in the O2 Sensor harness connector.

Is the resistance below 5.0 ohms?

Yes
1. Repair the short to ground in the (K299) O2 Sensor 1/2 Heater Control circuit.
2. Perform POWERTRAIN VERIFICATION TEST .
No
1. Go to 7).
7) (K902) O2 DOWN STREAM RETURN CIRCUIT

Fig 3: Measuring For Voltage On O2 Downstream Return Circuit
Courtesy of CHRYSLER LLC

Measure the voltage on the (K902) O2 Downstream Return 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 (K902) O2 Downstream Return 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 .