Page 936 of 5267

6.RESISTANCE IN THE (K900) SENSOR GROUND CIRCUIT
Turn the ignition off.
NOTE: Make sure the voltmeter leads meet the terminals in the
connector and that there is good terminal to wire connection.
NOTE: Make sure the voltmeter leads are connected for positive
polarity
Backprobe the (K900) Sensor ground circuit at the Battery Temperature
Sensor harness connector and the PCM harness connector using both
volt meter leads.
Start the engine.
Allow the engine to idle.
Is the voltage below 0.10 of a volt?
Ye s>>
Go To 8
No>>
Repair the excessive resistance in the (K900) Sensor
ground circuit.
Perform POWERTRAIN VERIFICATION TEST. (Refer to 9 -
ENGINE - STANDARD PROCEDURE)
7.(K25) BATTERY TEMP SENSOR SIGNAL CIRCUIT SHORTED TO GROUND
Turn the ignition off.
Disconnect the Battery Temp Sensor harness connector.
Disconnect the PCM harness connectors.
Measure the resistance between ground and the (K25) Battery Temp
Signal circuit.
Istheresistancebelow100ohms?
Ye s>>
Repair the short to ground in the (K25) Battery Temp Signal
circuit.
Perform POWERTRAIN VERIFICATION TEST. (Refer to 9 -
ENGINE - STANDARD PROCEDURE)
No>>
Go To 8
Page 939 of 5267

When Monitored:
With the engine RPM above 416 but less than 1500, the TPS voltage less than 1.13 volts, and battery voltage
greater than 10.4 volts.
Set Condition:
The MAP Sensor signal voltage is below 0.1 of a volt for 2.0 seconds with the engine running.
Possible Causes
(F855) 5-VOLT SUPPLY CIRCUIT OPEN
(F855) 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND
(K1) MAP SIGNAL CIRCUIT SHORTED TO GROUND
(K1) MAP SIGNAL CIRCUIT SHORTED TO THE (K900) SENSOR GROUND CIRCUIT
MAP SENSOR
PCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING).
Diagnostic Test
1.MAP SENSOR VOLTAGE BELOW 0.08 OF A VOLT
Ignition on, engine not running.
With a scan tool, read the MAP Sensor voltage.
Is the voltage below 0.08 of a volt?
Ye s>>
Go To 2
No>>
Refer to the INTERMITTENT CONDITION Diagnostic Procedure. (Refer to 9 - ENGINE - DIAGNOSIS
AND TESTING)
2.(F855) 5-VOLT SUPPLY CIRCUIT
Turn the ignition off.
Disconnect the MAP Sensor harness connector.
Ignition on, engine not running.
Measure the voltage on the (F855) 5-volt Supply circuit in the MAP Sen-
sor harness connector.
Is the voltage between 4.5 to 5.2 volts?
Ye s>>
Go To 3
No>>
Go To 6
Page 944 of 5267

When Monitored:
With the engine RPM above 400, the TPS voltage less than 1.13 volts, and battery voltage greater than 10.4
volts
Set Condition:
With the engine RPM above 400, the TPS voltage less than 1.13 volts, and battery voltage greater than 10.4
volts
Possible Causes
(K1) MAP SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE
(K1) MAP SIGNAL CIRCUIT OPEN
(K1) MAP SIGNAL CIRCUIT SHORTED TO THE (F856) 5-VOLT SUPPLY CIRCUIT
(K900) SENSOR GROUND CIRCUIT OPEN
MAP SENSOR
PCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING).
Diagnostic Test
1.MAP SENSOR VOLTAGE ABOVE 4.92 VOLTS
Start the engine.
With a scan tool, read the MAP Sensor voltage.
Is the voltage above 4.92 volts?
Ye s>>
Go To 2
No>>
Refer to the INTERMITTENT CONDITION Diagnostic Procedure. (Refer to 9 - ENGINE - DIAGNOSIS
AND TESTING)
2.MAP SENSOR
Turn the ignition off.
Disconnect the MAP Sensor harness connector.
Connect a jumper wire between the (K1) MAP Signal circuit and the
(K900) Sensor ground circuit in the Sensor harness connector.
Ignition on, engine not running.
With a scan tool, monitor the MAP Sensor voltage.
Is the voltage below 1.0 volt with the jumper wire installed?
Ye s>>
Replace the MAP Sensor.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 3
NOTE: Remove the jumper wire before continuing.
Page 945 of 5267

3.(K1) MAP SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE
Turn the ignition off.
Disconnect the C1 and C2 PCM harness connectors.
Ignition on, engine not running.
Measure the voltage on the (K1) MAP Signal circuit in the MAP Sensor
harness connector.
Is the voltage above 0 volts?
Ye s>>
Repair the short to battery voltage in the (K1) MAP Signal
circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 4
4.(K1) MAP SIGNAL CIRCUIT OPEN
Turn the ignition off.
CAUTION: Do not probe the PCM harness connectors. Probing the
PCM harness connectors will damage the PCM terminals resulting
in poor terminal to pin connection. Install Miller Special Tool #8815
to perform diagnosis.
Measure the resistance of the (K1) MAP Signal circuit from the MAP
Sensor harness connector to the appropriate terminal of special tool
#8815.
Is the resistance below 5.0 ohms?
Ye s>>
Go To 5
No>>
Repair the open in the (K1) MAP Signal circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
Page 953 of 5267

When Monitored:
With the ignition on and battery voltage greater than 10.4 volts.
Set Condition:
When the Inlet Air Temp Sensor Signal circuit voltage is less than 0.8 of a volt.
Possible Causes
(K21) IAT SIGNAL CIRCUIT SHORTED TO GROUND
(K21) IAT SIGNAL CIRCUIT SHORTED TO THE (K900) SENSOR GROUND CIRCUIT
INTAKE AIR TEMPERATURE SENSOR
PCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING).
Diagnostic Test
1.IAT SENSOR VOLTAGE BELOW 0.078 OF A VOLT
Ignition on, engine not running.
With a scan tool, read the IAT voltage.
Is the voltage below 0.078 of a volt?
Ye s>>
Go To 2
No>>
Refer to the INTERMITTENT CONDITION Diagnostic Procedure. (Refer to 9 - ENGINE - DIAGNOSIS
AND TESTING)
2.IAT SENSOR
Turn the ignition off.
Disconnect the IAT Sensor harness connector.
Ignition on, engine not running.
With a scan tool, read IAT voltage.
Is the voltage above 0.05 of a volt?
Ye s>>
Replace the Intake Air Temperature Sensor.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 3
Page 957 of 5267

When Monitored:
With the ignition on. Battery voltage greater than 10.4 volts.
Set Condition:
The Intake Air Temperature (IAT) sensor circuit voltage at the PCM goes above 4.98 volts for 2.8 seconds.
One Trip Fault. Three good trips to turn off the MIL.
Possible Causes
(K21) IAT SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE
(K21) IAT SIGNAL CIRCUIT OPEN
(K900) SENSOR GROUND CIRCUIT OPEN
IAT SENSOR
PCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING).
Diagnostic Test
1.IAT SENSOR VOLTAGE ABOVE 4.98 VOLTS
Ignition on, engine not running.
With a scan tool, read the Intake Air Temperature Sensor voltage.
Is the voltage above 4.98 volts?
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.IAT SENSOR
Turn the ignition off.
Disconnect the Intake Air Temperature Sensor harness connector.
Connect a jumper wire between the (K21) IAT Signal circuit and the
(K900) Sensor ground circuit in the IAT Sensor harness connector.
Ignition on, engine not running.
With a scan tool, read the IAT Sensor voltage.
Is the voltage below 1.0 volt with the jumper wire installed?
Ye s>>
Replace the IAT Sensor.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 3
NOTE: Remove the jumper wire before continuing.
Page 958 of 5267

3.(K21) IAT SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE
Disconnect the C2 PCM harness connector.
Ignition on, engine not running.
Measure the voltage on the (K21) IAT Signal circuit in the IAT Sensor
harness connector.
Is the voltage above 0 volts?
Ye s>>
Repair the short to battery voltage in the (K21) IAT Signal
circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 4
4.(K21) IAT SIGNAL CIRCUIT OPEN
Turn the ignition off.
CAUTION: Do not probe the PCM harness connectors. Probing the
PCM harness connectors will damage the PCM terminals resulting
in poor terminal to pin connection. Install Miller Special Tool #8815
to perform diagnosis.
Measure the resistance of the (K21) IAT Signal circuit from the IAT Sen-
sor harness connector to the appropriate terminal of special tool #8815.
Is the resistance below 5.0 ohms?
Ye s>>
Go To 5
No>>
Repair the open in the (K21) IAT Signal circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
Page 961 of 5267

Theory of Operation
The engine coolant temperature sensor is a negative temperature coefficient thermistor-type sensor whose resis-
tance varies inversely with temperature. At cold temperatures the sensorresistance is high so the voltage is high.
As the coolant temperature increases the resistance decreases and the voltage becomes low.
When Monitored:
With the ignition on. Battery voltage greater than 10.4 volts.
Set Condition:
The Engine Coolant Temperature (ECT) Signal circuit voltage at the PCM goes below 0.8 of a volt for more
than 3 seconds.
Possible Causes
(K2) ECT SIGNAL CIRCUIT SHORTED TO GROUND
(K2) ECT SIGNAL CIRCUIT SHORTED TO THE (K900) SENSOR GROUND CIRCUIT
ECT SENSOR
PCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING).
Diagnostic Test
1.ECT SENSOR VOLTAGE BELOW 1.0 OF A VOLT
Ignition on, engine not running.
With a scan tool, read the ECT voltage.
Is the voltage below 1.0 of a volt?
Ye s>>
Go To 2
No>>
Refer to the INTERMITTENT CONDITION Symptom. (Refer to 9 - ENGINE - DIAGNOSIS AND TEST-
ING)
2.ECT SENSOR
Turn the ignition off.
Disconnect the ECT harness connector.
Ignition on, engine not running.
With a scan tool, read ECT voltage.
Is the voltage above 1.0 volt?
Ye s>>
Replace the ECT Sensor.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 3