Page 996 of 5267

7.(K99) O2 SENSOR 1/1 HEATER CONTROL CIRCUIT OPEN
Turn the ignition off.
Disconnect the C3 PCM harness connector.
Measure the resistance of the (K99) O2 Sensor 1/1 Heater Control cir-
cuit from the O2 Sensor harness connector to the PCM harness con-
nector.
Is the resistance below 5.0 ohms?
Ye s>>
Go To 8
No>>
Repair the open in the (K99) O2 Sensor 1/1 Heater Control
Circuit (PWM) circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
8.PCM
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.
Were there any problems found?
Ye s>>
Repair as necessary.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No>>
Replace and program the Powertrain Control Module per Service Information.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
Page 1000 of 5267
P0135-O2 SENSOR 1/1 HEATER PERFORMANCE
For a complete wiring diagramRefer to Section 8W.
Page 1001 of 5267

When Monitored:
With battery voltage greater than 9 volts, at a cold start, ECT less than 147°F, battery temperature sensor
equal to or less than 27°F, and engine at idle for at least 12 seconds.
Set Condition:
O2 sensor voltage greater than 3 volts for 30 to 90 seconds.
Possible Causes
(K99) O2 1/1 HEATER CONTROL CIRCUIT OPEN
(K99) O2 1/1 HEATER CONTROL CIRCUIT SHORTED TO GROUND
(K343) O2 FUSED ASD RELAY OUTPUT CIRCUIT OPEN
(K343) O2 FUSED ASD RELAY OUTPUT CIRCUIT SHORTED TO GROUND
O2 SENSOR
PCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING).
Diagnostic Test
1.O2 SENSOR HEATER OPERATION
Turn the ignition off.
NOTE: Wait a minimum of 8 minutes to allow the O2 Sensor to cool down before continuing the test. Allow
the O2 Sensor voltage to stabilize between 4.6 and 5.0 volts.
Ignition on, engine not running.
With a scan tool, actuate the O2 Heater Test.
With the scan tool, monitor 1/1 O2 Sensor voltage for at least 2 minutes.
Does the voltage stay above 4.5 volts?
Ye s>>
Go To 2
No>>
Refer to the INTERMITTENT CONDITION Diagnostic Procedure. (Refer to 9 - ENGINE - DIAGNOSIS
AND TESTING)
2.O2 SENSOR HEATER ELEMENT
Turn the ignition off.
NOTE: Allow the O2 sensor to cool down to room temperature.
Disconnect the O2 Sensor harness connector.
Measure the resistance of the O2 Heater Element across the 1/1 O2 Sensor connector between the (K99) O2
Heater Control terminal and the (K343) Fused ASD relay output terminal.
NOTE: O2 Heater Element resistance values should be measured at 70°F (21.1°C). The resistance value will
vary with different temperature values.
Is the resistance of the O2 Sensor Heater Element between 3.3 and 4.1 ohms?
Ye s>>
Go To 3
No>>
Replace the O2 Sensor.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
Page 1002 of 5267

3.(K99) O2 1/1 HEATER CONTROL CIRCUIT OPEN
Disconnect the C3 PCM harness connector.
Measure the resistance of the (K99) O2 1/1 Heater Control circuit from
the O2 harness connector to the PCM harness connector.
Is the resistance below 5 ohmS?
Ye s>>
Go To 4
No>>
Repair the excessive resistance in the (K99) O2 1/1 Heater
Control circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
4.(K343) O2 1/1 FUSED ASD RELAY OUTPUT CIRCUIT OPEN
Measure the resistance of the (K343) O2 1/1 Fused ASD Relay Output circuit,from the relay terminal to the O2
Sensor harness connector.
Is the resistance below 5 ohms?
Ye s>>
Go To 5
No>>
Repair the excessive resistance in the (K343) O2 1/1 Fused ASD relay outputcircuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
5.(K343) O2 1/1 FUSED ASD RELAY OUTPUT CIRCUIT SHORTED TO GROUND
Measure the resistance between ground and the (K343) O2 1/1 Fused ASD RelayOutput circuit in the O2 Sensor
harness connector.
Is the resistance below 5 ohms?
Ye s>>
Repair the short to ground in the (K343) O2 1/1 Fused ASD Relay Output circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 6
6.PCM
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.
Were there any problems found?
Ye s>>
Repair as necessary.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No>>
Replace and program the Powertrain Control Module per Service Information.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
Page 1003 of 5267
P0136-O2 SENSOR 1/2 HEATER CIRCUIT MALFUNCTION
For a complete wiring diagramRefer to Section 8W.
Page 1004 of 5267

When Monitored:
Ignition ON, with battery voltage greater than 10.4 volts.
Set Condition:
The state of the PCM relay control circuit, between the PCM and relay coil, does not match the desired state.
Possible Causes
O2 SENSOR HEATER RELAY
(K343) FUSED ASD RELAY OUTPUT CIRCUIT
(K127) O2 HEATER RELAY CONTROL CIRCUIT OPEN
(K127) O2 HEATER RELAY CONTROL CIRCUIT SHORTED TO GROUND
O2 SENSOR
PCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
1.GOOD TRIP EQUAL TO ZERO
Ignition on, engine not running.
With the Scan Tool, read DTCs and record the related Freeze Frame data.
Is the Good Trip Counter displayed and equal to zero?
Ye s>>
Go To 2
No>>
Refer to the INTERMITTENT CONDITION Diagnostic Procedure. (Refer to 9 - ENGINE - STANDARD
PROCEDURE)
2.O2 SENSOR HEATER RELAY
Turn the ignition off.
Remove the Heater Relay from the PDC.
Measurement is taken at the Heater Relay component.
Measure the resistance of the O2 Sensor Heater Relay Coil.
Is the resistance above 100 ohms?
Ye s>>
Replace the O2 Sensor Heater Relay.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 3
3.(K344) FUSED ASD RELAY OUTPUT CIRCUIT
Ignition on, engine not running.
With the Scan Tool, actuate the ASD Relay.
Using a 12-volt test light connected to ground, probe the (K344) Fused ASD Relay Output circuit of the O2 Heater
Relay in the PDC.
Does the test light illuminate brightly when the relay actuates?
Ye s>>
Go To 4
No>>
Repair the open or short to ground in the ASD Relay Output circuit. Inspect the related fuse and repair
as necessary.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
Page 1005 of 5267

4.(K127) O2 HEATER RELAY CONTROL CIRCUIT OPEN
Turn the ignition off.
Disconnect the PCM harness connectors.
Measure the resistance of the (K127) O2 Heater Relay Control circuit from the PDC (Heater Relay) connector to the
PCM harness connector.
Is the resistance below 5.0 ohms?
Ye s>>
Go To 5
No>>
Repair the open in the (K127) O2 Heater Relay Control circuit.
Perform POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
5.(K127) O2 HEATER RELAY CONTROL CIRCUIT SHORTED TO GROUND
Measure the resistance between ground and the (K127) O2 Heater Relay Control circuit at the PDC connector.
Istheresistancebelow100ohms?
Ye s>>
Repair the short to ground in the (K127) O2 Sensor Heater Relay Control circuit.
Perform POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 6
6.O2 HEATER ELEMENT
NOTE: Allow the O2 Sensor to cool to room temperature.
Disconnect the O2 Sensor harness connector.
Measure the resistance across the O2 Sensor Heater element component side.
NOTE: The resistance value will increase with warmer temperatures.
Is the resistance between 4.0 and 5.0 ohms at 70° F (21.1°C)?
Ye s>>
Go To 7
No>>
Replace the O2 Sensor.
Perform POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
7.PCM
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 are not possible causes remaining, view repair.
Repair
Replace and program the Powertrain Control Module per Service Information.
Perform POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
Page 1007 of 5267

When Monitored:
At a cold start, engine coolant below 98°F, Ambient/Battery Sensor readingwithin27°F,andEngineCoolant
Temperature above 170°F on the previous key off.
Set Condition:
The Oxygen Sensor signal voltage is below 0.156 of a volt for 28 seconds after starting engine.
Possible Causes
(K141) O2 SENSOR 1/2 SIGNAL CIRCUIT SHORTED TO GROUND
(K141) O2 SENSOR 1/2 SIGNAL CIRCUIT SHORTED TO THE (K900) SENSOR GROUND CIRCUIT
(K141) O2 SENSOR 2/1 SIGNAL SHORTED TO THE (Z1) HEATER GROUND CIRCUIT
O2 SENSOR
PCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING).
Diagnostic Test
1.O2 SENSOR BELOW 0.16 OF A VOLT
Ignition on, engine not running.
With the scan tool, read DTCs and record the related Freeze Frame data.
Start the engine.
Allow the engine to idle for 4 to 5 minutes.
With the scan tool, read the O2 Sensor voltage.
Is the voltage below 0.16 of a volt?
Ye s>>
Go To 2
No>>
Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
2.O2 SENSOR OPERATION
WARNING: When the engine is operating, do not stand in a direct line with thefan. Do not put your hands
near the pulleys, belts, or fan. Do not wear loose clothing.
Disconnect the O2 Sensor harness connector.
Start the engine.
With the scan tool, monitor the O2 Sensor voltage.
IstheO2Sensorvoltageabove0.16ofavolt?
Ye s>>
Replace the O2 Sensor
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 3