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Home >> Mazda >> 2000 >> B2500 SX, Standard >> Repair and Diagnosis >> Engine Performance >> Engine Control Systems >> Engine Controls Trouble Shooting (2 Of 5) >> Intake Air Temperature (IAT) Sensor And Engine Coolant Temperature (ECT) Sensor

Intake Air Temperature (IAT) Sensor And Engine Coolant Temperature (ECT) Sensor

DTC P0112, P0113, P0117, P0118, P0125, P1112, P1116, P1117 DETECTION CONDITION AND POSSIBLE CAUSE

DTC P0112, P0113, P0117, P0118, P0125, P1112, P1116, P1117 INTAKE AIR TEMPERATURE (IAT) SENSOR ENGINE COOLANT TEMPERATURE (ECT) SENSOR
DETECTION CONDITION 
  • P0112 indicates the IAT sensor is less than the Self Test minimum of 0.2V or 250°F (121 °C).
  • P0113 indicates the IAT sensor is greater than the Self Test maximum of 4.6V or -46°F (-50°C).
  • P0117 indicates the ECT sensor is less than the Self Test minimum of 0.2V or 250°F (121°C).
  • P0118 indicates the ECT sensor is greater than the Self Test maximum of 4.6V or -46°F (-50°C).
  • P0125 indicates the ECT sensor has not achieved the required temperature level to enter closed loop operating conditions within a specified amount of time after starting engine.
  • P1112 indicates the IAT sensor signal was intermittent during the Comprehensive Component Monitor.
  • P1116 indicates the ECT sensor signal is out of Self Test range (0.3-3.7 V).
  • P1117 indicates the ECT circuit was intermittently open or shorted while engine was running.
NOTE:
  • Engine must be at normal operating temperature to pass KOEO Self-Test and KOER Self-Test.
  • Ambient temperature must be above 50°F (10°C) to receive acceptable input from IAT.
POSSIBLE CAUSE 
  • Overheating condition (P1116).
  • Damaged harness (P0112, P1112. P0113, P0117, P1117, P0118).
  • Improper harness connection (P0112, P0113, P0117, P0118).
  • Grounded circuit in harness (P0112, P0117).
  • Damaged PCM (P0112, P1112, P0113, P0117, P1117, P0118).
  • Damaged IAT or ECT sensor (P0112, P1112, P0113, P1116, P0117, P1117, P0118).
  • Insufficient warm-up time (P0125).
  • Low engine coolant level (P1116).
  • Poor thermostat operation (P1116).
  • Leaky or stuck open thermostat (P0125).
  • Damaged harness connector (P0112, P1112, P0113, P1116, P0117, P1117, P0118).
  • Open in IAT or ECT harness (P0113, P0118).
HINT  IAT Sensor Description 
  • Thermistor type (passive) sensor.
  • Provides air temperature information to PCM which uses the information as a correction factor in the calculation of fuel, spark and MARF.
  • Resistance changes with temperature. Electrical resistance decreases as temperature increases, and increases as temperature decreases.

ECT Sensor Description 
  • Thermistor type (passive) sensor.
  • Provides engine coolant temperature information to PCM.
  • Resistance changes with temperature. Electrical resistance decreases as temperature increases, and increases as temperature decreases.
G03988111Courtesy of MAZDA MOTORS CORP.
G03988112Courtesy of MAZDA MOTORS CORP.
G03988113Courtesy of MAZDA MOTORS CORP.
DTC P0112, P0113, P0117, P0118, P0125, P1112, P1116, P1117 INSPECTION

STEP INSPECTION ACTION
1
  • Was PCM Quick Test performed? 
 Yes For DTC P1116:
Go to step 2.
For KOEO or KOER DTC P0113 or P0118:
Go to step 6.
For KOEO or KOER DTC P0112 or P0117:
Go to step 10.
For Continuous Memory (without KOEO and KOER DTC's) DTC P0112, P0113, P0117, P0118, P1112 or P1117:
Go to step 13.
For DTC P0125:
Go to step 15.
No Perform PCM Quick Test.
2 DTC P1116: CHECK OPERATION OF ECT SENSOR
  • Run engine at 2000 rpm until engine temperature becomes stabilized
  • If vehicle does not start, go to step 4.
  • If vehicle stalls, refer to:

    See DIAGNOSTIC INDEX .

  • Verify upper radiator hose is hot and pressurized.
  • Run KOER Self Test.
  • Is DTC P1116 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 harness 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 sensor connector.
  • Measure resistance between ECT and SIG RTN at the ECT sensor harness connector.
  • Is resistance within specifications? 
 Yes For ECT sensor with a No Start:
Do not service DTC P1116 at this time.
See DIAGNOSTIC INDEX .
For symptoms of cooling fan concerns, overheating and lack of heat, do not service DTC P1116. Repair next DTC. If no other DTC exists, refer to:
See ENGINE COOLING SYMPTOM CHART .
All others:
Go to next step.
No Replace suspect ECT sensor.
Go to step 16.
5 CHECK RESISTANCE OF TEMPERATURE SENSOR WITH ENGINE RUNNING
NOTE: Verify that engine is at operating temperature before taking ECT readings.
  • Key OFF.
  • Disconnect suspect temperature sensor.
  • Run engine at 2, 000 rpm for two minutes.
  • Measure resistance between SIG and SIG RTN at the temperature sensor.
  • Is resistance within specifications? 
 Yes Replace PCM. See COMPUTERIZED ENGINE CONTROLS .
Go to step 16.
No Replace suspect sensor.
Go to step 16.
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 SIG and SIG RTN at the sensor connector.
  • Key ON, Engine OFF (KOEO)
    NOTE: If an NGS Tester communication concern exists, remove jumper wire immediately and go to step 9.
  • Access ECT V or IAT V PID.
  • Is ECT V or IAT V PID less than 0.2 V? 
 Yes Remove jumper wire.
Replace suspect sensor.
Go to step 16.
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 SIG at sensor harness connector and PCM test pin 38 (ECT) 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 COMPUTERIZED ENGINE CONTROLS .
Go to step 16.
No Repair open circuit.
Go to step 16.
9 CHECK TEMPERATURE SENSOR SIGNAL AND SIG RTN CIRCUITS FOR OPEN IN HARNESS
  • Measure resistance between SIG at sensor harness connector and PCM test pin 90 (VREF).
  • Is the resistance greater than 10K ohms? 
 Yes Replace PCM. See COMPUTERIZED ENGINE CONTROLS .
Go to step 16.
No Repair short to VREF.
Go to step 16.
10 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.
Go to step 16.
No Go to next step.
11 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) .
12 CHECK SIGNAL CIRCUIT FOR SHORT TO GROUND
  • Key OFF.
  • Disconnect PCM.
  • Disconnect suspect temperature sensor.
  • Install Breakout Box, leave PCM disconnected.
  • Measure resistance between the following PCM test pins:
    • 38 (ECT) or 39 (IAT) and 24 (PWR GND).
    • 38 (ECT) or 39 (IAT) and 91 (SIG RTN).
  • Is each resistance greater than 10K ohms? 
 Yes Replace PCM. See COMPUTERIZED ENGINE CONTROLS .
Go to step 16.
No Repair short circuit.
Go to step 16.
13 DTCS P0112, P1112, P0113, P0117, P1117 OR P0118: INTERMITTENT CHECK
  • Key OFF.
  • Key ON, Engine OFF (KOEO).
  • Monitor the ECT 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 voltage reading? 
 Yes Disconnect and inspect connectors.
If OK, replace sensor.
Go to step 16.
NOTE: For Continuous DTCs P1112 and P1117, refer to COMPREHENSIVE COMPONENT MONITOR DRIVE CYCLE .

See DRIVE CYCLES , .
No Go to next step.
14 CHECK ENGINE WIRING HARNESS
  • While observing the ECT 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 voltage reading? 
 Yes Isolate fault and repair as necessary.
Go to step 16.
NOTE: For Continuous DTCs P1112 and P1117, refer to COMPREHENSIVE COMPONENT MONITOR DRIVE CYCLE .

See DRIVE CYCLES .
No Go to step 16.
15 DTC P0125 INDICATES EXCESSIVE TIME TO ENTER CLOSED LOOP FUEL CONTROL
  • Is coolant level fill correct? 
 Yes See ENGINE COOLING SYMPTOM CHART .
No Fill to proper level.
NOTE: For Continuous DTCs P1112 and P1117, refer to COMPREHENSIVE COMPONENT MONITOR DRIVE CYCLE .

See DRIVE CYCLES .
Go to step 16.
16 VERIFY TROUBLESHOOTING OF DTCs COMPLETED
  • Make sure to reconnect all disconnected connectors.
  • Clear DTCs from PCM memory using NGS tester generic OBD-II function.
  • Perform PCM Quick Test.
  • Is same DTC present? 
 Yes Replace PCM. See COMPUTERIZED ENGINE CONTROLS .
Repeat 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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