Intention of troubleshooting procedure

WARNING: This page is about a different variant/trim than selected.

Step 1-2
- Perform an engine coolant-related inspection.
Step 3
- Perform an engine coolant passage assembly condition-related inspection.
Step 4
- Perform a unit inspection of the coolant control valve.
Step 5-6
- Perform a PCM input signal part-related inspection.
Repair completion verification
- Verify that the primary malfunction is resolved and there are no other malfunctions.

P0126-00: (PCM - VIN Y) TROUBLESHOOTING DIAGNOSTIC PROCEDURE

Step	Inspection	Results	Action
1	PURPOSE: DETERMINE IF ENGINE COOLANT USED AFFECTS CONDITION BY VERIFYING WITH CUSTOMER AND INSPECTING COLOR, ODOR, AND FOAMING DUE TO POSSIBILITY OF ENGINE COOLANT FREEZING IF ENGINE COOLANT CONCENTRATION IS LOW Is the specified engine coolant being used?	Yes	Go to the next step.
1		No	Replace the engine coolant and perform the repair completion verification 1. (Advise the customer to use specified engine coolant used.) (Refer to ENGINE COOLANT REPLACEMENT (VIN Y) in service information.)
2	PURPOSE: VERIFY THAT THERE IS NO ENGINE COOLANT LEAKAGE OR FOREIGN MATTER PENETRATION BECAUSE ECT SENSOR No. 1 MAY NOT MEASURE CORRECT TEMPERATURE DUE TO ENGINE COOLANT LEAKAGE Perform the "ENGINE COOLANT LEAKAGE INSPECTION". (Refer to ENGINE COOLANT LEAKAGE INSPECTION (VIN Y) in service information.) Is there engine coolant leakage or foreign matter penetration?	Yes	If there is engine coolant leakage: Repair or replace the malfunctioning location and refill the system with engine coolant. If there is foreign matter penetration: Replace engine coolant after removing the foreign matter. (Refer to ENGINE COOLANT REPLACEMENT (VIN Y) in service information.) Go to repair completion verification 1.
2		No	Go to the next step.
3	PURPOSE: VERIFY IF ENGINE COOLANT PASSAGE IS CORRECT BECAUSE CORRECT ENGINE COOLANT TEMPERATURE CANNOT BE DETERMINED IF ENGINE COOLANT PASSAGE IS INCORRECT Is the engine coolant passage (such as hose) connected correctly? (Ask customer if engine coolant passage has been serviced somewhere other than Authorized Mazda Dealer)	Yes	Go to the next step.
3		No	Connect engine coolant passage correctly and perform the repair completion verification 1.
4	PURPOSE: EXAMINE THERMOSTAT BECAUSE ENGINE COOLANT TEMPERATURE INCREASE SLOWS IF THERMOSTAT IS STUCK OPEN Inspect the thermostat. (Refer to THERMOSTAT INSPECTION (VIN Y) in service information.) Is there any malfunction?	Yes	Replace the thermostat and perform the repair completion verification 1. (Refer to THERMOSTAT REMOVAL/INSTALLATION (VIN Y) in service information.)
4		No	Go to the next step.
5	PURPOSE: EXAMINE ECT SENSOR No. 1 BECAUSE ENGINE COOLANT TEMPERATURE CANNOT BE MEASURED CORRECTLY IF ECT SENSOR No. 1 IS MALFUNCTIONING Inspect the ECT sensor No. 1. (Refer to ENGINE COOLANT TEMPERATURE (ECT) SENSOR INSPECTION (VIN Y) in service information.) Is there any malfunction?	Yes	Replace the ECT sensor No. 1 and perform the repair completion verification 1. (Refer to ENGINE COOLANT TEMPERATURE (ECT) SENSOR REMOVAL/INSTALLATION (VIN Y) in service information.)
5		No	Go to the next step.
6	PURPOSE: VERIFY ASSEMBLY CONDITION BECAUSE ENGINE COOLANT TEMPERATURE CANNOT BE MEASURED CORRECTLY IF ECT SENSOR No. 1 IS NOT ASSEMBLED CORRECTLY Verify the ECT sensor No. 1 assembly conditions. (Refer to ENGINE COOLANT TEMPERATURE (ECT) SENSOR REMOVAL/INSTALLATION (VIN Y) in service information.) Is the ECT sensor No. 1 assembled correctly?	Yes	Go to the next step.
6		No	Assemble the ECT sensor No. 1 correctly and perform the repair completion verification 1. (Refer to ENGINE COOLANT TEMPERATURE (ECT) SENSOR REMOVAL/INSTALLATION (VIN Y) in service information.)
Repair completion verification 1	PURPOSE: VERIFY THAT VEHICLE IS REPAIRED Install/connect the part removed/disconnected during the troubleshooting procedure. Clear the DTC recorded in the memory. (see CLEARING DTC .) Replicate the vehicle conditions at the time the DTC was detected using the following procedure. Implement the repeatability verification procedure. (See REPEATABILITY VERIFICATION PROCEDURE .) Perform the DTC inspection for the PCM. (See DTC INSPECTION .) Is the same Pending DTC present?	Yes	Refer to the controller area network (CAN) malfunction diagnosis flow to inspect for a CAN communication error. (See MALFUNCTION DIAGNOSIS FLOW [CONTROLLER AREA NETWORK (CAN)] .) If the CAN communication is normal, perform the diagnosis from Step 1. If the malfunction recurs, replace the PCM, then go to the next step. (Refer to applicable PCM REMOVAL/INSTALLATION (VIN Y) in the service information.)
Repair completion verification 1		No	Go to the next step.
Repair completion verification 2	PURPOSE: VERIFY IF OTHER DTCs DISPLAYED Perform the DTC inspection. (See DTC INSPECTION .) Are any other DTCs displayed?	Yes	Repair or replace the malfunctioning location according to the applicable DTC troubleshooting.
Repair completion verification 2		No	DTC troubleshooting completed.