Diagnostic procedure

WARNING: This page is about a different car, the 2005 Mazda RX-8. However, it is still accessible from the selected car via links, so may be relevant.

DTC P0118 DIAGNOSTIC PROCEDURE

STEP	INSPECTION		ACTION
1	VERIFY FREEZE FRAME DATA HAS BEEN RECORDED Has FREEZE FRAME DATA been recorded?	Yes	Go to the next step.
1		No	Record the FREEZE FRAME DATA 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.
2		No	Go to the next step.
3	INSPECT ECT SENSOR CONNECTOR FOR POOR CONNECTION Turn the ignition switch off. Disconnect the 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 8.
3		No	Go to the next step.
4	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 a possible short to power supply, then go to Step 8.
4		No	Go to the next step.
5	INSPECT ECT SENSOR Inspect the ECT sensor. (See ENGINE COOLANT TEMPERATURE (ECT) SENSOR INSPECTION .) Is there any malfunction?	Yes	Replace the ECT sensor, then go to Step 8. (See ENGINE COOLANT TEMPERATURE (ECT) SENSOR REMOVAL/INSTALLATION .)
5		No	Go to the next step.
6	INSPECT PCM CONNECTOR FOR POOR CONNECTION Turn the ignition switch off. 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 8.
6		No	Go to the next step.
7	INSPECT ECT SENSOR CIRCUIT FOR OPEN CIRCUIT Turn the ignition switch off. Inspect for continuity between the following circuits: ECT sensor terminal A (wiring harness-side) and PCM terminal 2K (wiring harness-side) ECT sensor terminal B (wiring harness-side) and PCM terminal 1U (wiring harness-side) Is there continuity?	Yes	Go to the next step.
7		No	Repair or replace the wiring harness for a possible open circuit, then go to the next step.
8	VERIFY TROUBLESHOOTING OF DTC P0118 COMPLETED Make sure to reconnect all disconnected connectors. Clear the DTC from the PCM memory using the WDS or equivalent. Start the engine. Is the same DTC present?	Yes	Replace the PCM, then go to the next step. (See PCM REMOVAL/INSTALLATION .)
8		No	Go to the next step.
9	VERIFY AFTER REPAIR PROCEDURE Perform the "AFTER REPAIR PROCEDURE". (See AFTER REPAIR PROCEDURE .) Are any DTCs present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE .)
9		No	DTC troubleshooting completed.