
Symptom:
P-0134 1/1 O2 SENSOR STAYS AT CENTER
When Monitored and Set Condition:
P-0134 1/1 O2 SENSOR STAYS AT CENTER
When Monitored: With the engine running for more than 2 minutes and engine
temperature greater than 76 degrees C (170 degrees F).
Set Condition: The Upstream Oxygen Sensor Signal voltage is between 0.35 volt and 0.55
volt for 1.5 minutes.
POSSIBLE CAUSES
O2 SENSOR 1/1 GROUND CIRCUIT OPEN
O2 SENSOR 1/1 SIGNAL CIRCUIT OPEN
1/1 O2 SENSOR WIRING HARN INTER DEFECT
1/1 O2 SENSOR WIRING HARN OBS DEFECT
O2 SENSOR 1/1 DEFECTIVE
PCM DEFECTIVE
TEST ACTION APPLICABILITY
1 Ignition Off
Start the engine and allow it to reach normal operating temperature.
With the DRB in actuator tests, set RPM to 1500.
In sensors, read the Upstream Oxygen Sensor State.
Is the Upstream O2 Sensor level switching?All
Ye s®Go To 2
No®Go To 4
2 Ignition Off
Start the engine and allow it to reach normal operating temperature.
Using the DRB, set the engine speed to 1500 RPM.
With the DRB, read the Upstream O2 Sensor level.
Wiggle Upstream O2 Sensor Connector and Harness.
While wiggling the Harness, monitor the DRB display.
At any time was the Upstream O2 Sensor state locked at center?All
Ye s®Repair the open Harness or Connector that caused the O2 Sensor
state to stay at center.
Perform Powertrain Verification Test VER-5A.
No®Go To 3
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DRIVEABILITY
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TEST ACTION APPLICABILITY
3 Ignition Off
Using the schematic as a guide, inspect the Wiring and Connectors.
Were any problems found?All
Ye s®Repair as necessary.
Perform Powertrain Verification Test VER-5A.
No®Test Complete.
4 Ignition Off
Disconnect the Upstream O2 Sensor Connector.
Note: Check connectors - Clean/repair as necessary.
Ignition on, engine not running.
Using an Ohmmeter, measure the resistance between the Upstream O2 Sensor
Ground Circuit and a good engine ground.
Is the resistance above 5.0 ohms?All
Ye s®Repair the open Upstream O2 sensor Ground Circuit.
Perform Powertrain Verification Test VER-5A.
No®Go To 5
5 Ignition Off
Disconnect the Upstream O2 Sensor Connector.
Note: Check connectors - Clean/repair as necessary.
Connect a jumper wire between the Upstream O2 Sensor Signal Circuit and B(+).
Ignition on, engine not running.
Using the DRB in sensors, read the Upstream Oxygen Sensor voltage.
Is the voltage above 1.0 volt?All
Ye s®Replace the Upstream O2 Sensor.
Perform Powertrain Verification Test VER-5A.
No®Go To 6
6 Ignition Off
Disconnect the Upstream O2 Sensor Connector.
Note: Check connectors - Clean/repair as necessary.
Disconnect the PCM Connector.
Note: Check connectors - Clean/repair as necessary.
Using an ohmmeter, measure the resistance of the Upstream O2 Sensor Signal
Circuit from the O2 Sensor Connector to the PCM Connector.
Is the resistance below 5.0 ohms?All
Ye s®Go To 7
No®Repair the open Upstream O2 Sensor Signal Circuit.
Perform Powertrain Verification Test VER-5A.
7 If there are no potential causes remaining, the PCM is assumed to be defective.
View repair options.All
Repair
Replace the PCM.
Perform Powertrain Verification Test VER-5A.
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DRIVEABILITY
P-0134 1/1 O2 SENSOR STAYS AT CENTER ÐContinued
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TEST ACTION APPLICABILITY
4 If there are no potential causes remaining, the Downstream O2 Sensor is assumed to
be defective.
View repair options.All
Repair
Replace the Upstream O2 Sensor.
Perform Powertrain Verification Test VER-5A.
5 Start the engine.
Wiggle Downstream O2 Sensor Connector and Harness.
While wiggling the Harness, watch the Downstream O2 Sensor voltage.
Did the O2 Sensor voltage go above 1.2 volts at any time?All
Ye s®Repair the Harness or Connector that has the intermittent short
to voltage.
Perform Powertrain Verification Test VER-5A.
No®Go To 6
6 Ignition Off
Using the schematic as a guide, inspect the Wiring and Connectors.
Were any problems found?All
Ye s®Repair as necessary.
Perform Powertrain Verification Test VER-5A.
No®Go To 7
7 Ignition Off
Disconnect the Downstream O2 Sensor.
Note: Check connectors - Clean/repair as necessary.
Inspect connectors.
Is any Terminal damaged, pushed out or miswired?All
Ye s®Repair as necessary.
Perform Powertrain Verification Test VER-5A.
No®Test Complete.
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DRIVEABILITY
P-0138 1/2 O2 SENSOR SHORTED TO VOLTAGE ÐContinued
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TEST ACTION APPLICABILITY
3 Turn Ignition On (Engine Off).
During the following voltage drop measurement, wiggle wires between O2S Connec-
tor and PCM Connector.
Using a voltmeter, backprobe O2S (Signal) Circuit between O2S Connector (O2S
Signal) and PCM Connector (O2S Signal).
While wiggling wires, is the voltage drop reading below 0.10 VDC?All
Ye s®Go To 4
No®Repair poor connection (high resistance) on O2S Signal Circuit.
Perform VERIFICATION TEST VER-5A3.
4 At this time the 1/2 O2S SLOW RESPONSE does not exist or is an intermittent
problem.
With the DRB, read the FREEZE FRAME DATA.
With this screen, attempt to duplicate the condition that has set this fault.
While using FREEZE FRAME DATA pay particular attention to the fault setting
conditions, such as speed, temp, load, and map vacuum.
Does the 1/2 O2S SLOW RESPONSE reoccur?All
Ye s®Go To 5
No®The 1/2 O2S SLOW RESPONSE no longer exists.
Perform VERIFICATION TEST VER-5A3.
5 The following are possible causes for O2 Sensor Slow Response: exhaust leak, fuel
contamination, O2 sensor failure, electrical wiring connectors, electrical mechanical,
and O2 heater failure.
Start the Engine.
NOTE: Check the exhaust for excessive smoke caused by oil or coolant
consumption.
Is there an oil or coolant consumption condition present?All
Ye s®Repair engine mechanical as necessary and replace O2 Sensor.
Perform VERIFICATION TEST VER-5A3.
No®Go To 6
6 The following are possible causes for O2 Sensor Slow Response: exhaust leak, fuel
contamination, O2 sensor failure, electrical wiring connectors, electrical mechanical,
and O2 heater failure.
Start the Engine.
Check the Exhaust System for leaks between the Engine and the catalyst.
Are there any leaks?All
Ye s®Repair or replace leaking Exhaust System as necessary.
Perform VERIFICATION TEST VER-5A3.
No®Go To 7
7 The following are possible causes for O2 Sensor Slow Response: exhaust leak, fuel
contamination, O2 sensor failure, electrical wiring connectors, electrical mechanical,
and O2 heater failure.
Turn Ignition On (Engine Off).
Using a voltmeter, backprobe O2S (Signal) Circuit between O2S Connector (O2S
Signal) and PCM Connector (O2S Signal).
Is the voltage drop reading below 0.10 VDC?All
Ye s®Go To 8
No®Repair poor connection (high resistance) on O2S Signal Circuit.
Perform VERIFICATION TEST VER-5A3.
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DRIVEABILITY
P-0139 1/2 O2S SLOW RESPONSE ÐContinued
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TEST ACTION APPLICABILITY
8 The following are possible causes for O2 Sensor Slow Response: exhaust leak, fuel
contamination, O2 sensor failure, electrical wiring connectors, electrical mechanical,
and O2 heater failure.
Turn Ignition On (Engine Off).
Using a voltmeter, backprobe O2S (Sensor Ground) Circuit between O2S Connector
(Sensor Ground) and PCM Connector (Sensor Ground).
Is the voltage drop reading below 0.10 VDC?All
Ye s®Replace the O2 Sensor.
Perform VERIFICATION TEST VER-5A3.
No®Repair poor connection (high resistance) on O2 Sensor Ground
Circuit.
Perform VERIFICATION TEST VER-5A3.
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DRIVEABILITY
P-0139 1/2 O2S SLOW RESPONSE ÐContinued
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Symptom:
P-0140 1/2 O2 SENSOR STAYS AT CENTER
When Monitored and Set Condition:
P-0140 1/2 O2 SENSOR STAYS AT CENTER
When Monitored: With the engine running for more than 2 minutes and engine
temperature greater than 76 degrees C (170 degrees F).
Set Condition: The Upstream Oxygen Sensor Signal voltage is between 0.35 volt and 0.55
volt for 1.5 minutes.
POSSIBLE CAUSES
O2 SENSOR 1/2 GROUND CIRCUIT OPEN
O2 SENSOR 1/2 SIGNAL CIRCUIT OPEN
1/2 O2 SENSOR WIRING HARN INTER DEFECT
1/2 O2 SENSOR WIRING HARN OBS DEFECT
O2 SENSOR 1/2 DEFECTIVE
PCM DEFECTIVE
TEST ACTION APPLICABILITY
1 Ignition Off
Start the engine and allow it to reach normal operating temperature.
With the DRB in actuator tests, set RPM to 1500.
In sensors, read the Downstream Oxygen Sensor Level.
Is the Downstream O2 Sensor Level switching?All
Ye s®Go To 2
No®Go To 4
2 Ignition Off
Start the engine and allow it to reach normal operating temperature.
Using the DRB, set the engine speed to 1500 RPM.
With the DRB, read the Downstream O2 Sensor state.
Wiggle Downstream O2 Sensor Connector and Harness.
While wiggling the Harness, monitor the DRB display.
At any time was the Downstream O2 Sensor state locked at center?All
Ye s®Repair the open Harness or Connector that caused the O2 Sensor
state to stay at center.
Perform Powertrain Verification Test VER-5A.
No®Go To 3
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DRIVEABILITY
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TEST ACTION APPLICABILITY
3 Ignition Off
Using the schematic as a guide, inspect the Wiring and Connectors.
Were any problems found?All
Ye s®Repair as necessary.
Perform Powertrain Verification Test VER-5A.
No®Test Complete.
4 Ignition Off
Disconnect the Downstream O2 Sensor Connector.
Note: Check connectors - Clean/repair as necessary.
Ignition on, engine not running.
Using an Ohmmeter, measure the resistance between the Downstream O2 Sensor
Ground Circuit and a good engine ground.
Is the resistance above 5.0 ohms?All
Ye s®Repair the open Downstream O2 sensor Ground Circuit.
Perform Powertrain Verification Test VER-5A.
No®Go To 5
5 Ignition Off
Disconnect the Downstream O2 Sensor Connector.
Note: Check connectors - Clean/repair as necessary.
Connect a jumper wire between the Downstream O2 Sensor Signal Circuit and B(+).
Ignition on, engine not running.
Using the DRB in sensors, read the Downstream Oxygen Sensor voltage.
Is the voltage above 1.0 volt?All
Ye s®Replace the Downstream O2 Sensor.
Perform Powertrain Verification Test VER-5A.
No®Go To 6
6 Ignition Off
Disconnect the Downstream O2 Sensor Connector.
Note: Check connectors - Clean/repair as necessary.
Disconnect the PCM Connector.
Note: Check connectors - Clean/repair as necessary.
Using an ohmmeter, measure the resistance of the Downstream O2 Sensor Signal
Circuit from the O2 Sensor Connector to the PCM Connector.
Is the resistance below 5.0 ohms?All
Ye s®Go To 7
No®Repair the open Downstream O2 Sensor Signal Circuit.
Perform Powertrain Verification Test VER-5A.
7 If there are no potential causes remaining, the PCM is assumed to be defective.
View repair options.All
Repair
Replace the PCM.
Perform Powertrain Verification Test VER-5A.
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DRIVEABILITY
P-0140 1/2 O2 SENSOR STAYS AT CENTER ÐContinued
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TEST ACTION APPLICABILITY
3 Ignition Off
Disconnect the Injector #1 Connector.
Note: Check connectors - Clean/repair as necessary.
Turn ignition on.
With the DRB, actuate the Auto Shutdown Relay.
Using a Voltmeter, measure the ASD Relay Output voltage.
Does the voltage cycle high and low?All
Ye s®Go To 4
No®Repair the open ASD Relay Output Circuit.
Perform Powertrain Verification Test VER-5A.
4 Ignition Off
Disconnect the Injector #1 Connector.
Note: Check connectors - Clean/repair as necessary.
Disconnect the Powertrain Control Module Connector.
Note: Check connectors - Clean/repair as necessary.
Use an Ohmmeter in the following step.
Measure the Injector #1 Driver Circuit from the PCM to the Injector.
Is the resistance below 5.0 ohms?All
Ye s®Go To 5
No®Repair the open Injector #1 Driver Circuit.
Perform Powertrain Verification Test VER-5A.
5 Ignition Off
Disconnect the Injector #1 Connector.
Note: Check connectors - Clean/repair as necessary.
Disconnect the Powertrain Control Module Connector.
Note: Check connectors - Clean/repair as necessary.
Using an Ohmmeter, measure the Injector #1 Driver Circuit.
Is the resistance below 5.0 ohms?All
Ye s®Repair the Injector #1 Driver Circuit for a short to ground.
Perform Powertrain Verification Test VER-5A.
No®Go To 6
6 If there are no potential causes remaining, the Powertrain Control Module is
assumed to be defective.
View repair options.All
Repair
Replace the Powertrain Control Module.
Perform Powertrain Verification Test VER-5A.
7 Ignition Off
Using the schematic as a guide, inspect the Wiring and Connectors.
Were any problems found?All
Ye s®Repair as necessary.
Perform Powertrain Verification Test VER-5A.
No®Go To 8
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DRIVEABILITY
P-0201 INJECTOR #1 CONTROL CIRCUIT ÐContinued
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