Theory of Operation
The General Temperature Rationality looks at the outputs of the three temperature sensors and compare them
under cold start conditions. Following a start to run delay time, the outputs of the ambient, engine coolant, and
intake air temperature sensors will be compared. If two sensors agree but not the third, the third sensor is declared
as irrational. If all three sensors are irrational the General Temperature Sensor Rationality is failed.
When Monitored:
Ignition on and battery voltage greater than 10 volts.
Set Condition:
Ambient Air, Engine Coolant, and Intake Air Temp sensor inputs are compared under cold start conditions.
After start up the temp readings are monitored. If two of the three readingsagree and the third doesn’t, a DTC
is stored. Two Trip Fault. Three good trips to turn off the MIL.
Possible Causes
EXCESSIVE RESISTANCE IN THE SENSOR SIGNAL CIRCUIT
EXCESSIVE RESISTANCE IN THE (K900) SENSOR GROUND CIRCUIT
EXCESSIVE RESISTANCE IN THE (G930) AAT RETURN CIRCUIT
TEMPERATURE SENSOR
PCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING).
Diagnostic Test
1.ACTIVE DTC
Ignition on, engine not running.
With a scan tool, read the DTCs.
NOTE: All ECT, Intake Air, and Ambient Air Temperature Sensor codes must bediagnosed and repaired
before continuing.
NOTE: In cold weather, this DTC could be set by a high powered block heater andnorepairwouldbe
required.
Is the DTC active at this time?
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.TEMPERATURE SENSOR CIRCUIT
With a scan tool, read the ECT, Ambient Air Temp, and Intake Air Temp Sensor temp values.
Start the engine.
Allow the engine to reach normal operating temperature while monitoring the three Sensor temperature values.
Is the temperature for each of the Sensors increasing properly?
Ye s>>
Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 3
When Monitored:
With the engine running in closed loop mode, the ambient/battery temperature above (-7°C) 20°F, altitude
below 8500 ft.
Set Condition:
If the PCM multiplies short term compensation by long term adaptive as wellas a purge fuel multiplier and the
result is below a certain value for 30 seconds over two trips, a freeze frameis stored, the MIL illuminates and
a trouble code is stored. Two Trip Fault. Three good trips to turn off the MIL.
Possible Causes
EXHAUST LEAK
ENGINE MECHANICAL
1/2O2SENSOR
(K141) O2 SENSOR 1/2 SIGNAL CIRCUIT
(K299) O2 1/2 HEATER CONTROL CIRCUIT
(K904) O2 RETURN DOWNSTREAM CIRCUIT
FUEL CONTAMINATION
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING).
Diagnostic Test
1.ACTIVE DTC
NOTE: Check the vehicle repair history. If the 1/2 O2 has been replaced makesure 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 sil-
icone, oil and coolant.
Ignition on, engine not running.
With a scan tool, read DTCs.
Is the DTC active at this time?
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.EXHAUST LEAK
Turn the ignition off.
WARNING: To avoid personal injury from the exhaust system being hot, allowthe 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?
Ye s>>
Go To 3
No>>
Repair or Replace as necessary.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
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?
Ye s>>
Go To 6
No>>
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.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
6.(K299) O2 SENSOR 1/2 HEATER CONTROL CIRCUIT SHORTED TO GROUND
Turn the ignition off.
Disconnect the C3 PCM harness connector.
Measure the resistance between ground and the (K299) O2 Sensor 1/2
Heater Control circuit from the O2 Sensor harness connector.
Is the resistance below 5.0 ohms?
Ye s>>
Repair the short to ground in the (K299) O2 Sensor 1/2
Heater Control circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 7
When Monitored:
With the engine running in closed loop mode, the ambient/battery temperature above (-7°C) 20°F, altitude
below 8500 ft.
Set Condition:
If the PCM multiplies short term compensation by long term adaptive as wellas a purge fuel multiplier and the
result is below a certain value for 30 seconds over two trips, a freeze frameis stored, the MIL illuminates and
a trouble code is stored. Two Trip Fault. Three good trips to turn off the MIL.
Possible Causes
EXHAUST LEAK
ENGINE MECHANICAL
1/2O2SENSOR
(K141) O2 SENSOR 1/2 SIGNAL CIRCUIT
(K299) O2 HEATER 1/2 CONTROL CIRCUIT
(K904) O2 RETURN DOWNSTREAM CIRCUIT
FUEL CONTAMINATION
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING).
Diagnostic Test
1.ACTIVE DTC
NOTE: Check the vehicle repair history. If the 1/2 O2 has been replaced makesure 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 sil-
icone, oil and coolant.
Ignition on, engine not running.
With a scan tool, read DTCs.
Is the DTC active at this time?
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.EXHAUST LEAK
Turn the ignition off.
WARNING: To avoid personal injury from the exhaust system being hot, allowthe 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?
Ye s>>
Go To 3
No>>
Repair or Replace as necessary.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
6.(K299) O2 SENSOR 1/2 HEATER CONTROL CIRCUIT OPEN
Turn the ignition off.
Disconnect the C3 PCM harness connector.
Measure the resistance of the (K299) O2 Sensor 1/2 Heater Control cir-
cuit from the O2 Sensor harness connector to the appropriate terminal
of special tool #8815.
Is the resistance below 5.0 ohms?
Ye s>>
Go To 7
No>>
Repair the open in the (K299) O2 Sensor 1/2 Heater Con-
trol circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
7.(K904) O2 RETURN DOWNSTREAM CIRCUIT
Measure the voltage on the (K904) O2 Return Downstream circuit in the
O2 Sensor harness connector.
Is the voltage at 2.5 volts?
Ye s>>
Check the fuel system for contaminants.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
No>>
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.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
When Monitored:
With the engine running in closed loop mode, the ambient/battery temperature above (-7°C) 20°F, altitude
below 8500 ft and fuel level greater than 15%.
Set Condition:
If the PCM multiplies short term compensation by long term adaptive and a certain percentage is exceeded for
two trips, a freeze frame is stored, the MIL illuminates and a trouble code is stored. Two Trip Fault. Three good
trips to turn off the MIL.
Possible Causes
EXHAUST LEAK
ENGINE MECHANICAL
2/2O2SENSOR
(K243) O2 2/2 SIGNAL CIRCUIT
(K399) O2 HEATER 2/2 CONTROL CIRCUIT
(K904) O2 RETURN DOWNSTREAM CIRCUIT
FUEL CONTAMINATION
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING).
Diagnostic Test
1.ACTIVE DTC
NOTE: Check the vehicle repair history. If the 2/2 O2 has been replaced makesure 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 sil-
icone, oil and coolant.
Ignition on, engine not running.
With a scan tool, read DTCs.
Is the DTC active at this time?
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.EXHAUST LEAK
Turn the ignition off.
WARNING: To avoid personal injury from the exhaust system being hot, allowthe 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?
Ye s>>
Go To 3
No>>
Repair or Replace as necessary.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
5.(K243) O2 SENSOR 2/2 SIGNAL CIRCUIT
Remove the jump wire.
Ignition on, engine not running.
With the scan tool, monitor the O2 Sensor voltage.
Is the voltage above 4.8 volts?
Ye s>>
Go To 6
No>>
Check the (K243) O2 Sensor 2/2 Signal circuit for a 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.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
6.(K399) O2 SENSOR 2/2 HEATER CONTROL CIRCUIT SHORTED TO GROUND
Turn the ignition off.
Disconnect the C3 PCM harness connector.
Measure the resistance between ground and the (K399) O2 Sensor 2/2
Heater Control circuit in the O2 Sensor harness connector.
Is the resistance below 5.0 ohms?
Ye s>>
Repair the short to ground in the (K399) O2 Sensor 2/2
Heater Control circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 7
When Monitored:
With the engine running in closed loop mode, the ambient/battery temperature above (-7°C) 20°F, altitude
below 8500 ft.
Set Condition:
If the PCM multiplies short term compensation by long term adaptive as wellas a purge fuel multiplier and the
result is below a certain value for 30 seconds over two trips, a freeze frameis stored, the MIL illuminates and
a trouble code is stored. Two Trip Fault. Three good trips to turn off the MIL.
Possible Causes
EXHAUST LEAK
ENGINE MECHANICAL
2/2O2SENSOR
(K342) O2 SENSOR 2/2 SIGNAL CIRCUIT
(K399) O2 SENSOR 2/2 HEATER CONTROL CIRCUIT
(K904) O2 RETURN DOWNSTREAM CIRCUIT
FUEL CONTAMINATION
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING).
Diagnostic Test
1.ACTIVE DTC
NOTE: Check the vehicle repair history. If the 2/2 O2 has been replaced makesure 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 sil-
icone, oil and coolant.
Ignition on, engine not running.
With a scan tool, read DTCs.
Is the DTC active at this time?
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.EXHAUST LEAK
Turn the ignition off.
WARNING: To avoid personal injury from the exhaust system being hot, allowthe 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?
Ye s>>
Go To 3
No>>
Repair or Replace as necessary.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)