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Home >> Mazda >> 2005 >> Tribute i, FWD, Standard >> Repair and Diagnosis >> Engine Performance >> Symptom Troubleshooting [Engine Control System] >> Intake Air Temperature (IAT) Sensor And Engine Coolant Temperature (ECT) Sensor / Cylinder Head Temperature (CHT) Sensor
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Intake Air Temperature (IAT) Sensor And Engine Coolant Temperature (ECT) Sensor / Cylinder Head Temperature (CHT) Sensor

NOTE: The following test procedures are for DTCs P0110, P0111, P0112, P0113, P0115, P0117, P0118, P0125, P0128, P0298, P1110, P1112, P1113, P1116, P1117, P1285, P1288, P1289, P1290, P1299 and P1798.
Fig 1: Intake Air Temperature (IAT) Sensor And Engine Coolant Temperature (ECT) Sensor Detection Condition Possible Cause
G03723661Courtesy of MAZDA MOTORS CORP.
Fig 2: Identifying Voltage And Temperature Graph
G03723662Courtesy of MAZDA MOTORS CORP.
Fig 3: Identifying Intake Air Temperature Sensor
G03723663Courtesy of MAZDA MOTORS CORP.
Fig 4: IAT Typical Diagnostic Reference Values Chart
G03723664Courtesy of MAZDA MOTORS CORP.
Fig 5: Cylinder Head Temperature Sensor Expected Values Chart
G03723665Courtesy of MAZDA MOTORS CORP.
INTAKE AIR TEMPERATURE INSPECTION/ACTION CHART

STEP INSPECTION ACTION
1
  • Was PCM Quick Test performed? 
 Yes For DTC P1116 or P1288:
Go to next step.
For DTC 1285 (if not cooling system malfunction):
Go to step 4.
For KOEO or KOER DTC P0113 or P0118:
Go to step 6.
For DTC P1289 or P1290:
Go to step 10.
For KOEO or KOER DTC P0112 or P0117:
Go to step 11.
For Continuous Memory (without KOEO and KOER DTC's) DTC P0112, P0113, P0117, P0118, P1112 or P1117, P1289, P1290:
Go to step 14.
For DTC P0125 or P0128:
Go to step 16.
For DTC P1299:
Go to step 17.
No Perform PCM Quick Test. See PCM QUICK TEST  .
2 DTC P1116, P1288: CHECK OPERATION OF ECT / CHT SENSOR
  • Run engine at 2,000 rpm until engine temperature becomes stabilized.
  • If vehicle does not start, Go to step 4.
  • If vehicle stalls, see DIAGNOSTIC INDEX  .
  • Verify upper radiator hose is hot and pressurized.
  • Run KOER Self-Test.
  • Is DTC P1116 or P1288 present? 
 Yes Go to next step.
No Engine was not in closed loop operating conditions. Repair any other DTCs as necessary.
3 CHECK VREF CIRCUIT VOLTAGE AT TP SENSOR
  • Key OFF.
  • Disconnect Throttle Position (TP) sensor connector.
  • Key ON, Engine OFF (KOEO).
  • Measure voltage between VREF and SIG RTN at TP sensor harness connector.
  • Is the voltage between 4.0 and 6.0 V? 
 Yes Go to next step.
No See TEST 1: VEHICLE REFERENCE VOLTAGE (VREF)  .
4 CHECK RESISTANCE OF TEMPERATURE SENSOR WITH ENGINE OFF
  • Key OFF.
  • Reconnect TP sensor.
  • Disconnect ECT or CHT sensor connector.
  • Measure resistance between ECT / CHT and SIG RTN at the ECT / CHT sensor harness connector.
  • Is resistance within specifications? 
 Yes For ECT / CHT sensor with a No Start:
Do not service DTC P1116 or P1288 at this time.
See DIAGNOSTIC INDEX  .
For symptoms of cooling fan concerns, overheating and lack of heat, do not service DTC P1116 or P1288. Repair next DTC. If no other DTC exists,
SYMPTOM TROUBLESHOOTING CHART - ENGINE COOLING SYSTEM  .
All others:
Go to next step.
No Replace ECT / CHT sensor.
See ENGINE COOLANT TEMPERATURE (ETC) SENSOR -- 3. or CYLINDER HEAD TEMPERATURE (CHT) SENSOR -- 2.3 .
Go to step 18.
5 CHECK RESISTANCE OF TEMPERATURE SENSOR WITH ENGINE RUNNING
NOTE:
  • Verify that engine is at operating temperature before taking ECT / CHT readings.
  • Key OFF.
  • Disconnect suspect temperature sensor.
  • Run engine at 2,000 rpm for two minutes.
  • Measure resistance between ECT / CHT / IAT and SIG RTN at the temperature sensor.
  • Is resistance within specifications? 
 Yes Replace PCM.
See POWERTRAIN CONTROL MODULE (PCM) .
Go to step 18.
No Replace ECT / CHT / IAT sensor.
See ENGINE COOLANT TEMPERATURE (ETC) SENSOR -- 3. , CYLINDER HEAD TEMPERATURE (CHT) SENSOR -- 2.3 or MASS AIR FLOW (MAF) SENSOR -- 2.3L .
Go to step 18.
6 DTC P0118 OR P0113: CHECK VOLTAGE BETWEEN VREF AND SIG RTN
  • Key OFF.
  • Disconnect TP sensor.
  • Key ON, Engine OFF (KOEO).
  • Measure voltage between VREF and SIG RTN at the TP sensor harness connector.
  • Is the voltage between 4.0 and 6.0 V? 
 Yes Go to next step.
No See TEST 1: VEHICLE REFERENCE VOLTAGE (VREF)  .
7 SIMULATE OPPOSITE SIGNAL TO PCM
  • Key OFF.
  • Disconnect suspect temperature sensor connector.
  • Connect jumper wire between ECT / CHT / IAT and SIG RTN at the sensor connector.
  • Key ON, Engine OFF (KOEO)
    NOTE:
    • If a WDS or equivalent tester communication concern exists, remove jumper wire immediately and go to step 9.
  • Access ECT V or IAT V PID.
  • Is ECT V, CHT V, or IAT V PID less than 0.2 V? 
 Yes Remove jumper wire.
Replace suspect sensor.
See ENGINE COOLANT TEMPERATURE (ETC) SENSOR -- 3. , CYLINDER HEAD TEMPERATURE (CHT) SENSOR -- 2.3 or MASS AIR FLOW (MAF) SENSOR -- 2.3L .
Go to step 18.
No Remove jumper wire.
Go to next step.
8 CHECK TEMPERATURE SENSOR SIGNAL AND SIG RTN CIRCUITS FOR OPEN IN HARNESS
  • Key OFF.
  • Disconnect PCM.
  • Disconnect suspect temperature sensor.
  • Install Breakout Box, leave PCM disconnected.
  • Measure resistance between ECT / CHT / IAT at sensor harness connector and PCM test pin 38 (ECT / CHT) or 39 (IAT).
  • Measure resistance between SIG RTN at sensor harness connector and PCM test pin 91.
  • Is each resistance less than 5.0 ohms? 
 Yes Replace PCM.
See POWERTRAIN CONTROL MODULE (PCM) .
Go to step 18.
No Repair open circuit.
Go to step 18.
9 CHECK TEMPERATURE SENSOR SIGNAL AND SIG RTN CIRCUITS FOR OPEN IN HARNESS
  • Measure resistance between ECT / CHT / IAT at sensor harness connector and PCM test pin 90 (VREF).
  • Is the resistance greater than 10K ohms? 
 Yes Replace PCM.
See POWERTRAIN CONTROL MODULE (PCM) .
Go to step 18.
No Repair short to VREF.
Go to step 18.
10 DTC P1289 OR P1290: CHECK VOLTAGE OF CHT PID
  • Key ON, Engine OFF (KOEO).
  • Access CHT V PID.
  • Is CHT V PID less than 0.2 V? 
 Yes Go to next step.
No Go to step 7.
11 DTC P0112 OR P0117: SIMULATE OPPOSITE SIGNAL TO PCM
  • Key OFF.
  • Disconnect suspect temperature sensor.
  • Key ON, Engine OFF (KOEO).
  • Access ECT V or IAT V PID.
  • Is ECT V or IAT V PID more than 4.6 V? 
 Yes Replace sensor.
See ENGINE COOLANT TEMPERATURE (ETC) SENSOR -- 3.
Go to step 18.
No Go to next step.
12 CHECK VREF CIRCUIT VOLTAGE AT TP SENSOR
  • Key OFF.
  • Disconnect TP sensor.
  • Key ON, Engine OFF (KOEO).
  • Measure voltage between VREF and SIG RTN at TP sensor harness connector.
  • Is the voltage between 4.0 and 6.0 V? 
 Yes There is sufficient VREF voltage. Reconnect TP sensor connector.
Go to next step.
No Reconnect TP sensor connector.
See TEST 1: VEHICLE REFERENCE VOLTAGE (VREF)  .
13 CHECK SIGNAL CIRCUIT FOR SHORT TO GROUND
  • Key OFF.
  • Disconnect suspect temperature sensor.
  • Install Breakout Box, leave PCM disconnected.
  • Measure resistance between the following PCM test pins:
    • 38 (ECT / CHT) or 39 (IAT) and 24 (PWR GND).
    • 38 (ECT / CHT) or 39 (IAT) and 91 (SIG RTN).
  • Is each resistance greater than 10K ohms? 
 Yes Replace PCM.
See POWERTRAIN CONTROL MODULE (PCM) .
Go to step 18.
No Repair short circuit.
Go to step 18.
14 DTCS P0112, P1112, P0113, P0117, P1117 OR P0118: INTERMITTENT CHECK
  • Key OFF.
  • Key ON, Engine OFF (KOEO).
  • Monitor the ECT V / CHT V PID or IAT V PID.
  • While observing the PID, perform the following:
    • Tap on sensor to simulate road shock.
    • Wiggle sensor connector.
  • Is there any large change in the temperature reading? 
 Yes Disconnect and inspect connectors.
If OK, replace sensor.
See ENGINE COOLANT TEMPERATURE (ETC) SENSOR -- 3. , CYLINDER HEAD TEMPERATURE (CHT) SENSOR -- 2.3 or MASS AIR FLOW (MAF) SENSOR -- 2.3L
Go to step 18.
NOTE:

See DRIVE CYCLE  .
No Go to next step.
15 CHECK ENGINE WIRING HARNESS
  • Key ON, Engine OFF (KOEO).
  • While observing the ECT V / CHT V or IAT V PID, perform the following:
    • Hold vehicle harness close to sensor connector. Wiggle, shake and bend small sections of wiring harness while working toward PCM.
  • Is there any change in the temperature reading? 
 Yes Isolate fault and repair as necessary.
Go to step 18.
NOTE:

See DRIVE CYCLE  .
No Go to step 18.
16 DTC P0125 OR P0128 INDICATES EXCESSIVE TIME TO ENTER CLOSED LOOP FUEL CONTROL
  • Is coolant level fill correct? 
 Yes See SYMPTOM TROUBLESHOOTING CHART - ENGINE COOLING SYSTEM  .
No Fill to proper level.
NOTE:

DRIVE CYCLE  .
Go to step 18.
17 DTC P1299 INDICATES AN ENGINE OVERHEAT CONDITION OCCURRED
  • Check engine coolant level.
  • Is coolant level fill correct? 
 Yes See PINPOINT TEST 2: THE ENGINE OVERHEATS  .
No See PINPOINT TEST 1: LOSS OF COOLANT  .
18 VERIFY TROUBLESHOOTING OF DTCs COMPLETED
  • Make sure to reconnect all disconnected connectors.
  • Clear DTCs from PCM memory using WDS or equivalent tester generic OBD II function.
  • Perform PCM Quick Test. See PCM QUICK TEST  .
  • Is same DTC present? 
 Yes Replace PCM.
See POWERTRAIN CONTROL MODULE (PCM) .
Repeat PCM Quick Test. See PCM QUICK TEST  .
No If any other DTC is present, go to applicable DTC inspection.
If no DTC is present, troubleshooting complete.
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