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2008 - MX-5 - Engine

DTC P0118 [LF]



DTC P0118

ECT sensor circuit high input

DETECTION CONDITION

  • The PCM monitors the ECT sensor signal at PCM terminal 2AH. If the PCM detects the ECT sensor voltage is above 4.58 V, the PCM determines that the ECT sensor circuit has malfunction.

    Diagnostic support note
  • This is a continuous monitor (Engine cooling system).

  • The MIL illuminates if the PCM detects the above malfunction condition during first drive cycle.

  • PENDING CODE is available if the PCM detects the above malfunction condition.

  • FREEZE FRAME DATA is available.

  • The DTC is stored in the PCM memory.

POSSIBLE CAUSE

  • ECT sensor malfunction

  • Connect or terminal malfunction

  • Open circuit in wiring harness between ECT sensor terminal A and PCM terminal 2AH

  • Short to power supply in wiring harness between ECT sensor terminal A and PCM terminal 2AH

  • Open circuit in wiring harness between ECT sensor terminal B and PCM terminal 2AY

  • PCM malfunction


Diagnostic procedure

STEP

INSPECTION

ACTION

1

VERIFY FREEZE FRAME DATA AND DIAGNOSTIC MONITORING TEST RESULTS HAVE BEEN RECORDED
  • Have FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS (Engine cooling system related) been recorded?

Yes

Go to the next step.

No

Record the FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS on the repair order, then go to the next step.

2

VERIFY RELATED REPAIR INFORMATION AVAILABILITY
  • Verify related Service Bulletins and/or on-line repair information availability.

  • Is any related repair information available?

Yes

Perform repair or diagnosis according to the available repair information.

  • If the vehicle is not repaired, go to the next step.

No

Go to the next step.

3

INSPECT POOR CONNECTION OF ECT SENSOR CONNECTOR
  • Turn the ignition switch off.

  • Disconnect ECT sensor connector.

  • Inspect for poor connection (such as damaged/pulled-out pins, corrosion).

  • Is there any malfunction?

Yes

Repair or replace the terminal, then go to Step 9.

No

Go to the next step.

4

CLASSIFY ECT SENSOR MALFUNCTION OR WIRING HARNESS MALFUNCTION
  • Connect the M-MDS to the DLC-2.

  • Access ECT PID.

  • Connect a jumper wire between ECT sensor terminals A and B (wiring harness-side).

  • Verify the ECT value.

  • Is the voltage 4.58 V or below?

Yes

Replace the ECT sensor, then go to Step 9.

(See ENGINE COOLANT TEMPERATURE (ECT) SENSOR REMOVAL/INSTALLATION [LF].)

No

Go to the next step.

5

INSPECT ECT SENSOR SIGNAL CIRCUIT FOR SHORT TO POWER SUPPLY
  • Turn the ignition switch to the ON position (Engine off).

  • Measure the voltage between ECT sensor terminal A (wiring harness-side) and body ground.

  • Is the voltage B+?

Yes

Repair or replace the wiring harness for short to power supply, then go to Step 9.

No

Go to the next step.

6

INSPECT PCM CONNECTOR FOR POOR CONNECTION
  • Disconnect the PCM connector.

  • Inspect for poor connection (such as damaged/pulled-out pins, corrosion).

  • Is there any malfunction?

Yes

Repair or replace the terminal, then go to Step 9.

No

Go to the next step.

7

INSPECT ECT SENSOR SIGNAL CIRCUIT FOR OPEN CIRCUIT
  • Inspect the continuity between ECT sensor terminal A (wiring harness-side) and PCM terminal 2AH.

  • Is there continuity?

Yes

Go to the next step.

No

Repair or replace the wiring harness for open circuit, then go to Step 9.

8

INSPECT ECT SENSOR GROUND CIRCUIT FOR OPEN CIRCUIT
  • Inspect for continuity between ECT sensor terminal B (wiring harness-side) and PCM terminal 2AY.

  • Is there continuity?

Yes

Go to the next step.

No

Repair or replace the wiring harness for open circuit, then go to the next step.

9

VERIFY TROUBLESHOOTING OF DTC P0118 COMPLETED
  • Make sure to reconnect all disconnected connectors.

  • Clear the DTC from the PCM memory using the M-MDS.

  • Start the engine, or perform the KOEO self-test with M-MDS.

    (See KOEO/KOER SELF TEST [LF].)

  • Is the same DTC present?

Yes

Replace the PCM, then go to the next step.

(See PCM REMOVAL/INSTALLATION [LF].)

No

Go to the next step.

10

VERIFY AFTER REPAIR PROCEDURE

Yes

Go to the applicable DTC troubleshooting.

(See DTC TABLE [LF].)

No

Troubleshooting completed.




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