Diagnostic procedure

DTC P0126, P0128 DIAGNOSTIC PROCEDURE

STEP	INSPECTION		ACTION
1	VERIFY FREEZE FRAME DATA AND DIAGNOSTIC MONITORING TEST RESULTS HAVE BEEN RECORDED Have the FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS (Engine cooling system related) been recorded?	Yes	Go to the next step.
1		No	Record FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS on the repair order, then go to the next step.
2	VERIFY RELATED REPAIR INFORMATION AVAILABILITY Check for related Service Bulletins and/or online repair information availability. Is any related repair information available?	Yes	Perform the 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 FOR OTHER DTCS Have other DTCs been stored?	Yes	Repair the circuit malfunction for applicable DTCs.
3	INSPECT FOR OTHER DTCS Have other DTCs been stored?	No	Go to the next step.
4	INSPECT IF COOLANT THERMOSTAT IS STUCK OPEN Perform the coolant thermostat inspection. (See THERMOSTAT INSPECTION ). Is the coolant thermostat normal?	Yes	Inspect the ECT sensor. Replace the ECT sensor if necessary, then go to the next step.
4		No	Replace the coolant thermostat, then go to the next step.
5	VERIFY MONITORING CONDITION FOR REPAIR VERIFICATION Make sure to reconnect all disconnected connectors. Cool down the engine. NOTE: If the temperature difference between the inside and outside of the workshop, the PCM might not operate the thermostat monitor. Therefore, it is recommended to cool down the engine outside of the workshop. Turn the ignition switch to the ON position (Engine off). Clear the DTC from the PCM memory using the WDS or equivalent. Access the ECT, IAT PIDs and make sure that each value is within the following specifications. ECT: below 36°C {97°F} (for P0128 only) Difference between the ECT and IAT: Below 6°C {43°F} Is there any PID that is out of specification?	Yes	Take corrective action (e.g. cool down engine), then repeat this step.
5		No	Go to the next step for DTC P0126 or go to Step 7 for DTC P0128.
6	VERIFY TROUBLESHOOTING OF DTC P0126 COMPLETED Start the engine and turn off the E/L and A/C. Access the DIAGNOSTIC MONITORING TEST RESULTS using the WDS or equivalent and monitor TEST #10: E1: 81 (ECT). NOTE: This test requires actual driving. A chassis roller cannot be used for this test. During the test drive, constant speed should be maintained, although 2 or 3 stops during every 5 minutes of driving time (e.g. for traffic signals) is acceptable. Stop-and-go (e.g. in case of traffic congestion) is not acceptable during the test period. Test period depends on ECT at engine start, (e.g. if ECT is -10°C {14°F} , monitoring period is 20 minutes and if ECT is 30°C {86°F} , monitoring period is 8 minutes ) Verify TEST #10: E1: 81 (ECT) value. Is the value above the minimum value?	Yes	Go to Step 8.
6		No	Replace PCM, then go to Step 8. (See PCM REMOVAL/INSTALLATION ).
7	VERIFY TROUBLESHOOTING OF DTC P0128 COMPLETED Start the engine and turn off the E/L and A/C. Access DIAGNOSTIC MONITORING TEST RESULTS using the WDS or equivalent and monitor TEST #10: E1: 80 (Heat radiation ratio) or #10: E1: 81 (ECT). NOTE: This test requires actual driving. A chassis roller cannot be used for this test. During the test drive, constant speed should be maintained, although 2 or 3 stops (e.g. for traffic signals) is acceptable. Stop-and-go (e.g. in case of traffic congestion) is not acceptable during the test period. Verify TEST #10: E1: 80 (Heat radiation ratio) and #10: E1: 81 (ECT) value. Is value of TEST #10: E1: 80 (Heat radiation ratio) below the maximum the value and value of TEST #10: E1:81 (ECT) above the minimum value?	Yes	Go to the next step.
7		No	Replace the PCM, then go to the next step. (See PCM REMOVAL/INSTALLATION ).
8	VERIFY AFTER REPAIR PROCEDURE Perform "AFTER REPAIR PROCEDURE". (See AFTER REPAIR PROCEDURE ). Are any DTCs present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE ).
8		No	Troubleshooting completed.