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.
61
DRIVEABILITY
P-0134 1/1 O2 SENSOR STAYS AT CENTER ÐContinued
ProCarManuals.com
TEST ACTION APPLICABILITY
4 Disconnect the 1/1 O2 Sensor Connector.
Check connectors - Clean / repair as necessary.
Is any terminal corroded, damaged, pushed out or miswired?All
Ye s®Repair or replace as necessary.
Perform VERIFICATION TEST VER-5A3.
No®Go To 5
5 Turn Ignition On (Engine Off).
Disconnect the 1/1 O2 Sensor Connector.
Check connectors - Clean / repair as necessary.
With the DRB, actuate the ASD Relay.
Using a voltmeter, measure the ASD Relay Output Circuit at the O2 Sensor
Connector (harness side).
Is the voltage above 10.0 volts?All
Ye s®Go To 6
No®Repair the open ASD Relay Output Circuit.
Perform VERIFICATION TEST VER-5A3.
6 Disconnect the 1/1 O2 Sensor Connector.
Check connectors - Clean / repair as necessary.
Using an ohmmeter, measure the O2 Sensor Heater Element at the O2 Sensor
Connector (component side).
Is the resistance between 4 and 7 ohms?All
Ye s®Go To 7
No®Replace the 1/1 O2 Sensor.
Perform VERIFICATION TEST VER-5A3.
7 Disconnect the 1/1 O2 Sensor Connector.
Check connectors - Clean / repair as necessary.
Using an ohmmeter, measure from the Heater Ground Circuit to ground at the O2
Sensor Connector (harness side).
Is the resistance below 5.0 ohms?All
Ye s®Replace the 1/1 O2 Sensor.
Perform VERIFICATION TEST VER-5A3.
No®Repair the open 1/1 O2 Sensor Ground Circuit.
Perform VERIFICATION TEST VER-5A3.
63
DRIVEABILITY
P-0135 O2S HEATER FAILURE ÐContinued
ProCarManuals.com
Symptom:
P-0138 1/2 O2 SENSOR SHORTED TO VOLTAGE
When Monitored and Set Condition:
P-0138 1/2 O2 SENSOR SHORTED TO VOLTAGE
When Monitored: With the engine running for more than 2 minutes and coolant
temperature above 76 degrees C (170 degrees F).
Set Condition: The Downstream Oxygen Sensor Signal voltage is above 1.2 volts.
POSSIBLE CAUSES
1/2 O2 SENSOR SIGNAL CIRCUIT SHORT TO VOLTAGE
1/2 O2 SEN HARNESS INTERMITTENT SHORT TO VOLTAGE
1/2 O2 SENSOR CONNECTOR OBSERVABLE DEFECT (A)
1/2 O2 SENSOR CONNECTOR OBSERVABLE DEFECT (B)
1/2 O2 SENSOR HARNESS OBSERVABLE DEFECT
1/2 O2 SENSOR DEFECTIVE
TEST ACTION APPLICABILITY
1 Start the engine.
With the DRB, read the Downstream O2 Sensor voltage.
Is the Downstream O2 Sensor voltage above 1.2 volts?All
Ye s®Go To 2
No®Go To 5
2 Ignition Off
Disconnect the Downstream O2 Sensor.
Note: Check connectors - Clean/repair as necessary.
Start the engine.
With the DRB, read the Downstream O2 Sensor Voltage.
Is the Upstream O2 Sensor voltage above 1.2 volts?All
Ye s®Repair the Downstream O2 Sensor Signal Circuit for a short to
voltage. If ok, replace the PCM.
Perform Powertrain Verification Test VER-5A.
No®Go To 3
3 Ignition Off
Disconnect the Downstream O2 Sensor.
Note: Check connectors - Clean/repair as necessary.
Is any Terminal damaged, pushed out or miswired?All
Ye s®Repair or replace as necessary.
Perform Powertrain Verification Test VER-5A.
No®Go To 4
66
DRIVEABILITY
ProCarManuals.com
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.
67
DRIVEABILITY
P-0138 1/2 O2 SENSOR SHORTED TO VOLTAGE ÐContinued
ProCarManuals.com
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.
69
DRIVEABILITY
P-0139 1/2 O2S SLOW RESPONSE ÐContinued
ProCarManuals.com
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.
72
DRIVEABILITY
P-0140 1/2 O2 SENSOR STAYS AT CENTER ÐContinued
ProCarManuals.com
TEST ACTION APPLICABILITY
4 Disconnect the 1/2 O2 Sensor Connector.
Check connectors - Clean / repair as necessary.
Is any terminal corroded, damaged, pushed out or miswired?All
Ye s®Repair or replace as necessary.
Perform VERIFICATION TEST VER-5A3.
No®Go To 5
5 Turn Ignition On (Engine Off).
Disconnect the 1/2 O2 Sensor Connector.
Check connectors - Clean / repair as necessary.
With the DRB, actuate the ASD Relay.
Using a voltmeter, measure the ASD Relay Output Circuit at the O2 Sensor
Connector (harness side).
Is the voltage above 10.0 volts?All
Ye s®Go To 6
No®Repair the open ASD Relay Output Circuit.
Perform VERIFICATION TEST VER-5A3.
6 Disconnect the 1/2 O2 Sensor Connector.
Check connectors - Clean / repair as necessary.
Using an ohmmeter, measure the O2 Sensor Heater Element at the O2 Sensor
Connector (component side).
Is the resistance between 4 and 7 ohms?All
Ye s®Go To 7
No®Replace the 1/2 O2 Sensor.
Perform VERIFICATION TEST VER-5A3.
7 Disconnect the 1/2 O2 Sensor Connector.
Check connectors - Clean / repair as necessary.
Using an ohmmeter, measure from the Heater Ground Circuit to ground at the O2
Sensor Connector (harness side).
Is the resistance below 5.0 ohms?All
Ye s®Replace the 1/2 O2 Sensor.
Perform VERIFICATION TEST VER-5A3.
No®Repair the open 1/2 O2 Sensor Ground Circuit.
Perform VERIFICATION TEST VER-5A3.
74
DRIVEABILITY
P-0141 1/2 O2S HEATER FAILURE ÐContinued
ProCarManuals.com
TEST ACTION APPLICABILITY
11 Check for any of the following conditions/mechanical problems.
ENGINE VACUUM Ð must be at least 13 inches in neutral
ENGINE VALVE TIMING Ð must be within specifications
ENGINE COMPRESSION Ð must be within specifications
ENGINE EXHAUST SYSTEM Ð must be free of any restrictions or leaks
ENGINE PVC SYSTEM Ð must flow freely
TORQUE CONVERTER STALL SPEED Ð must be within specifications
POWER BRAKE BOOSTER Ð no internal vacuum leaks
FUEL- must be free of contamination
FUEL INJECTOR Ð plugged or restricted injector; control wire not connected to
correct injector.
Are there any engine mechanical problems?All
Ye s®Repair as necessary.
Perform FUEL SYSTEM/MISFIRE MONITOR VERIFICATION
TEST
No®Go To 12
12 Turn ignition off.
Warning: The fuel system is under constant pressure (even with the engine
off). Before testing or servicing any fuel system hose, fitting or line, the fuel
system pressure must be released.
Disconnect the fuel supply line at the fuel rail.
Connect fuel line adapter #6539(5/169) or #6631 (3/89) to the disconnected fuel supply
line. Insert the other end of the adapter into a graduated container.
Caution: Do not operate the fuel pump for more than 7 seconds in the next
step. Fuel pump module reservoir may run empty and damage to the fuel
pump may result.
Specification: A good fuel pump will deliver at least 1/4 liter of fuel in 7
seconds.
With the DRB, actuate the ASD Fuel System test for 7 seconds.
Is the fuel pump capacity within specification?All
Ye s®Test Complete.
No®Check for a kinked/damaged fuel supply line between the fuel
tank and fuel rail. If OK, replace the fuel filter/pressure regulator.
Caution: Stop ALL Actuations.
13 The conditions required to set the DTC are no longer present.
With the DRB read and record the freeze frame data and the ªFuel System Similar
Conditions Windowº data.
Utilize the data and try to duplicate the operating conditions at which the DTC was
set. Pay particular attention to the ECT and RPM for added diagnostics.
Note: Refer to any TSB's that may apply to the symptom.
Test Complete
Repair
Test Complete.
78
DRIVEABILITY
P-0171±1/1 FUEL SYSTEM LEAN ÐContinued
ProCarManuals.com