DL: Cylinder Head Temperature (CHT) Sensor

DL: Introduction See: Diagnostic Trouble Code Tests and Associated Procedures\SECTION 5: Pinpoint Tests\DL: Cylinder Head Temperature (CHT) Sensor - Introduction

DL1 DTC P1288 OR P1116: CHECK OPERATION OF CYLINDER HEAD TEMPERATURE SENSOR

• Run engine at 2000 rpm until engine temperature becomes stabilized.
• No Starts or Vehicle that Stalls:
• GO to DL3.
• Check that upper radiator hose is hot and pressurized.
• Rerun Key On Engine Running (KOER) Self-Test.

Is DTC P1288 or P1116 present?
Yes

• GO to DL2

.

No

• Engine temperature was not stabilized. REPAIR any other DTCs

as necessary.

DL2 CHECK VREF CIRCUIT VOLTAGE AT TP SENSOR

• Disconnect throttle position (TP) sensor.

Note: GO to Pinpoint Test DH See: DH: Throttle Position (TP) Sensor - Introduction and refer toPinpoint Test Schematics and Connectors for TP harness connector pin-out information.

• Key on, engine off.
• Measure the voltage between VREF and SIG RTN circuits at the TP sensor harness connector.

Is voltage between 4.0 volts and 6.0 volts?
Yes

• There is sufficient VREF voltage. RECONNECT TP sensor. GO to DL3

.

No

• GO to C1 See: C: Reference Voltage - Pinpoint Test

.

DL3 CHECK RESISTANCE OF CYLINDER HEAD TEMPERATURE SENSOR WITH ENGINE OFF

• Disconnect CHT sensor.
• Measure resistance between CHT signal and SIG RTN pins at the CHT sensor. Refer to the table at the beginning of this pinpoint test for resistance specifications.

Is resistance within specification?
Yes

• For No Starts or Stalls, RETURN to Section 3, Symptom Charts. See: Symptom Related Diagnostic Procedures
• All others, GO to DL4

.

No

• REPLACE CHT sensor.

DL4 CHECK RESISTANCE OF CHT SENSOR WITH ENGINE RUNNING

Note: Verify that engine is at operating temperature before taking CHT readings.

• Run engine for two minutes at 2000 rpm.
• Measure resistance between CHT signal and SIG RTN pins at the CHT sensor. Refer to the table at the beginning of this Pinpoint Test for resistance specifications.
• Key off.

Is resistance within specification?
Yes

• REPLACE PCM (refer to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM) See: Programming and Relearning\Flash Electrically Eraseable Programmable Read Only Memory - Flash EEPROM).

No

• REPLACE CHT sensor.

DL5 DTC P1289 OR P1290: ACCESS CHT PID AND CHECK VOLTAGE

• Connect scan tool.
• Key on, engine off.
• Access CHT V PID.

Is the CHT V PID less than 0.2 volt?
Yes

• GO to DL6

.

No

• GO to DL7

.

DL6 CHECK FOR GROUNDED CIRCUIT

• Disconnect CHT sensor.
• Key on.
• Access CHT V PID.

Is the CHT V PID more than 4.6 volts?
Yes

• REPLACE CHT sensor.

No

• GO to DL21

.

DL7 CHECK FOR OPEN HARNESS

• Disconnect CHT sensor.
• Connect a jumper wire between the CHT signal and SIG RTN circuits at the CHT sensor vehicle harness connector.
• Key on.

-
Note: If a Scan Tool communication concern exists, remove jumper wire immediately and GO to DL12.

• Access CHT V PID.

Is the CHT V PID less than 0.2 volt?
Yes

• REPLACE CHT sensor.

No

• REMOVE jumper wire. GO to DL11

0. KEY OFF.

DL10 DTC P0118: SIMULATE OPPOSITE SIGNAL TO PCM

• Disconnect CHT sensor.
• Connect a jumper wire between the CHT signal circuit and SIG RTN circuit at the CHT sensor vehicle harness connector.
• Connect scan tool.
• Key on.

-
Note: If a Scan Tool communication concern exists, remove jumper wire immediately and GO to DL12.

• Access CHT V PID.

Is the CHT V PID less than 0.2 volt?
Yes

• REPLACE CHT sensor.

No

• REMOVE jumper wire. GO to DL11

.

DL11 CHECK CHT SENSOR SIGNAL AND SIG RTN CIRCUITS FOR OPEN IN HARNESS

Note: Refer to the PCM connector pin numbers in the beginning of this pinpoint test.

• Disconnect PCM.
• Measure resistance of CHT circuit between PCM harness connector pin and CHT sensor harness connector.
• Measure resistance of SIG RTN circuit between PCM harness connector pin and CHT sensor harness connector.

Is each resistance less than 5.0 ohms?
Yes

• REPLACE PCM (refer to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM) See: Programming and Relearning\Flash Electrically Eraseable Programmable Read Only Memory - Flash EEPROM).

No

• REPAIR open circuits.

DL12 CHECK CHT SENSOR SIGNAL FOR SHORT TO VREF IN HARNESS

• Key off.
• Disconnect PCM.
• Measure resistance between CHT and VREF circuits at the PCM harness connector.

Is resistance greater than 10,000 ohms?
Yes

• REPLACE PCM (refer to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM) See: Programming and Relearning\Flash Electrically Eraseable Programmable Read Only Memory - Flash EEPROM).

No

• REPAIR short to VREF.

DL20 DTC P0117: SIMULATE OPPOSITE SIGNAL TO PCM

• Disconnect CHT sensor.
• Connect scan tool.
• Key on.
• Access CHT V PID.

Is the CHT V PID more than 4.6 volts?
Yes

• REPLACE CHT sensor.

No

• GO to DL21

.

DL21 CHECK VREF CIRCUIT VOLTAGE AT TP SENSOR

• Disconnect throttle position (TP) sensor.

Note: GO to Pinpoint Test DH See: DH: Throttle Position (TP) Sensor - Introduction and refer toPinpoint Test Schematics and Connectors for TP harness connector pin-out information.

• Key on, engine off.
• Measure voltage between VREF and SIG RTN circuits at the TP sensor harness connector.

Is voltage between 4.0 and 6.0 volts?
Yes

• There is sufficient VREF voltage. RECONNECT TP sensor. GO to DL22

0. KEY OFF.

No

• GO to C1 See: C: Reference Voltage - Pinpoint Test

.

DL22 CHECK CHT SIGNAL CIRCUIT FOR SHORT TO GROUND

Note: Refer to the PCM connector pin numbers in the beginning of this pinpoint test.

• Disconnect PCM.
• Measure resistance between CHT signal and SIG RTN circuits and then between CHT signal and PWR GND circuits at the PCM harness connector.

Is each resistance greater than 10,000 ohms?
Yes

• REPLACE PCM (refer to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM) See: Programming and Relearning\Flash Electrically Eraseable Programmable Read Only Memory - Flash EEPROM).

No

• REPAIR short circuit.

DL30 DTC P1285: EARLY WARNING OF ENGINE OVERHEAT CONDITION

An engine overheat condition was sensed by the CHT sensor.

• Check cooling system for:
• Correct coolant level.
• Internal or external coolant leaks.
• Blockage of radiator.
• Cooling fan operation.

Note: If electric cooling fan does not operate, return to Section 3 See: Symptom Related Diagnostic Procedures for electric cooling fan DTC or symptom diagnosis.
Is cooling system OK?
Yes

• CHECK CHT sensor operation. GO to DL3

.

No

• REPAIR as necessary. REFER to Engine Cooling, for symptom diagnosis of Engine Overheats or Loss of Coolant.

DL40 ENGINE TEMPERATURE WARNING INDICATOR LAMP ON OR TEMPERATURE GAUGE INDICATES HOT, BUT ENGINE IS NOT OVERHEATING

Note: PCM Quick Test must be performed prior to entering this Pinpoint Test.
Was PCM Quick Test performed prior to entering this Pinpoint Test?
Yes

• No Diagnostic Trouble Codes (DTCs) received during PCM Quick

Test. GO to DL41
.

No

• GO to Section 3 See: Symptom Related Diagnostic Procedures and RERUN Quick Test. REPAIR any

DTCs as necessary.

DL41 ENGINE TEMPERATURE INDICATOR LAMP ON OR TEMPERATURE GAUGE INDICATES HOT, WITH NO DIAGNOSTIC TROUBLE CODE (DTC)

The Engine Temperature Warning Indicator (gauge or lamp) is a warning of an engine overheating condition. The PCM monitors the cylinder head temperature (CHT) sensor and grounds the engine temperature warning circuit when the engine is overheating. This causes the instrument cluster indicator to illuminate and/or forces the temperature gauge to H (hot) zone. A DTC P1285 will also be stored in the PCM.
This test diagnoses Engine Temperature Warning Lamp ON and/or temperature gauge in the H (hot) zone with no PCM DTCs.
Possible causes:

• Damaged engine coolant temperature sensor.
• Instrument cluster concern.
• Wiring harness fault between PCM and Instrument cluster. (PCM output pins: 19, 42 or 45 depending on vehicle application.)
• Damaged PCM.
• Disconnect PCM.
• Key on.

Is the engine temperature warning indicator lamp OFF and the temperature gauge in the normal zone with the PCM disconnected?
Yes

• Key off. REPLACE the PCM (refer to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM) See: Programming and Relearning\Flash Electrically Eraseable Programmable Read Only Memory - Flash EEPROM

).

No

• The PCM has not attempted to ground the Engine Temperature Warning

circuit and turn the engine temperature indicator lamp ON or force the temperature
gauge to the H (hot) zone. REFER to Instrument Panel, Gauges and Warning Indicators for further diagnosis.

DL80 P0116: CHECK TEMPERATURE SENSOR RESISTANCE WITH ENGINE OFF

Note: Verify that engine temperature is at ambient room temperature before continuing with this test. A soak period of 6 hours may be required. Refer to Diagnostic Trouble Code (DTC) Descriptions See: A L L Diagnostic Trouble Codes ( DTC )\Testing and Inspection\Diagnostic Trouble Code Descriptions, in Section 4 for information concerning P0116.

• Key on, engine off.
• Disconnect CHT sensor.
• Measure CHT sensor resistance. Refer to the chart at the beginning of this Pinpoint Test for resistance specifications.

Is resistance within specification?
Yes

• GO to DL81

.

No

• REPLACE suspect sensor.

DL81 P0116: CHECK TEMPERATURE SENSOR RESISTANCE WITH ENGINE RUNNING

Note: Verify that engine is at operating temperature before taking CHT readings.

• Run engine for two minutes at 2000 rpm.
• Measure temperature sensor resistance. Refer to the chart at the beginning of this Pinpoint Test for resistance specifications.

Is resistance within specification?
Yes

• Fault is not present at this time. COMPLETE OBDII Drive Cycle

to determine if Fuel, HEGO, Catalyst and Misfire monitors can be executed
(REFER to Section 2, Drive Cycles See: Diagnostic Trouble Code Tests and Associated Procedures\SECTION 2: Diagnostic Methods\Drive Cycles). Retest
if necessary.

No

• REPLACE suspect sensor.

DL90 DTCS P0117, P0118, P1117, P1289 OR P1290: INTERMITTENT CHECK

• Connect scan tool.
• Key on.
• Monitor the CHT PID.
• While observing the PID, complete the following:
• Tap on the sensor to simulate road shock.
• Wiggle the sensor connector.

Is there any large change in the temperature reading?
Yes

• Key off. DISCONNECT and INSPECT connectors. If OK, REPLACE CHT

sensor. COMPLETE OBDII Drive Cycle to verify repair (REFER to Section 2, Drive Cycles See: Diagnostic Trouble Code Tests and Associated Procedures\SECTION 2: Diagnostic Methods\Drive Cycles
).

No

• GO to DL91

.

DL91 CHECK ELECTRONIC ENGINE CONTROL (EC) WIRING HARNESS

• Still monitoring PID.
• While observing the appropriate PID, complete the following:
• Hold the vehicle harness close to the sensor connector. Wiggle, shake and bend small sections of wiring harness while working toward the PCM.

Is there any change in the temperature reading?
Yes

• ISOLATE fault. REPAIR as necessary. COMPLETE OBDII Drive Cycle

to verify repair (REFER to Section 2, Drive Cycles See: Diagnostic Trouble Code Tests and Associated Procedures\SECTION 2: Diagnostic Methods\Drive Cycles).

No

• GO to DL92

.

DL92 CHECK PCM AND VEHICLE HARNESS CONNECTOR

• Disconnect PCM.
• Disconnect CHT sensor.

Are connectors and terminals OK?
Yes

• Fault is not present at this time. COMPLETE OBDII Drive Cycle

(REFER to Section 2, Drive Cycles See: Diagnostic Trouble Code Tests and Associated Procedures\SECTION 2: Diagnostic Methods\Drive Cycles).

No

• REPAIR as necessary. COMPLETE OBDII Drive Cycle to verify repair

(REFER to Section 2, Drive Cycles See: Diagnostic Trouble Code Tests and Associated Procedures\SECTION 2: Diagnostic Methods\Drive Cycles).

DL100 DTC P1299 OR P0217 INDICATES AN ENGINE OVERHEAT CONDITION OCCURRED

Note: Refer to Section 4 See: A L L Diagnostic Trouble Codes ( DTC )\Testing and Inspection\Diagnostic Trouble Code Descriptions for possible causes and additional DTC description information.
WARNING: TO AVOID PERSONAL INJURY, DO NOT UNSCREW THE COOLANT PRESSURE RELIEF CAP WHILE THE ENGINE IS OPERATING OR HOT. THE COOLING SYSTEM IS UNDER PRESSURE; STREAM AND HOT LIQUID CAN COME OUT FORCEFULLY WHEN THE CAP IS LOOSENDED SLIGHTLY.

• Check engine coolant level.

Is the engine coolant level fill correct?
Yes

• REFER to Engine Cooling for symptom, Engine Overheats.

No

• REFER to Engine Cooling, for symptom, Loss of Engine Coolant.

DL110 DTC P0125: CHECK ENGINE COOLANT LEVEL

Diagnostic Trouble Code (DTC) P0125 indicates the CHT sensor has not achieved the required temperature level to enter closed loop operating conditions within a specified amount of time after starting engine. This DTC will light the MIL.
Possible causes:

• Insufficient warm up time.
• Leaky or stuck open thermostat.
• Low engine coolant level.
• Malfunctioning CHT sensor.

WARNING: TO AVOID PERSONAL INJURY, DO NOT UNSCREW THE COOLANT PRESSURE RELIEF CAP WHILE THE ENGINE IS OPERATING OR HOT. THE COOLING SYSTEM IS UNDER PRESSURE; STREAM AND HOT LIQUID CAN COME OUT FORCEFULLY WHEN THE CAP IS LOOSENDED SLIGHTLY.

• Check engine coolant level.

Is the engine coolant level fill correct?
Yes

• Go to Engine Cooling for further diagnostics.

No

• FILL engine coolant to proper level. Complete Comprehensive

Component Monitor Repair Verification Drive Cycle (Refer to Section 2 See: Diagnostic Trouble Code Tests and Associated Procedures\SECTION 2: Diagnostic Methods
,
Drive Cycles).