DTC P128A:00 [MZI-3.7]

id0102d2505700

DTC P128A:00 | CHT sensor circuit intermittent/erratic
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DETECTION CONDITION | • Indicates the CHT circuit became intermittently open or short while the engine was running.
POSSIBLE CAUSE | • CHT sensor connector or terminals malfunction • Short to ground in wiring harness between CHT sensor terminal A and PCM terminal 2AV • PCM connector or terminals malfunction • Short to power supply in wiring harness between CHT sensor terminal A and PCM terminal 2AV • Open circuit in wiring harness between the following terminals: ― CHT sensor terminal A—PCM terminal 2AV ― CHT sensor terminal B—PCM terminal 2G • CHT sensor malfunction • PCM malfunction

Diagnostic procedure

STEP | INSPECTION | ACTION
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1 | VERIFY RELATED SERVICE INFORMATION AVAILABILITY • Verify related Service Information availability. • Is any related Service Information available? | Yes | Perform repair or diagnosis according to the available Service Information. • If the vehicle is not repaired, go to the next step.
No | Go to the next step.
2 | INSPECT CHT SENSOR CONNECTOR CONDITION • Turn the ignition switch off. • Disconnect the CHT sensor connector. • Inspect for poor connection (such as damaged/pulled-out pins, corrosion). • Is there any malfunction? | Yes | Repair or replace the connector and/or terminals, then go to Step 8.
No | Go to the next step.
3 | INSPECT CHT SENSOR CIRCUIT FOR SHORT TO GROUND • CHT sensor connector is disconnected. • Inspect for continuity between CHT sensor terminal A (wiring harness-side) and body ground. • Is there continuity? | Yes | If the short to ground circuit could be detected: • Repair or replace the wiring harness for a possible short to ground. If the short to ground circuit could not be detected: • Replace the PCM (short to ground in the PCM internal circuit). (See PCM REMOVAL/INSTALLATION [MZI-3.7].) Go to Step 8.
No | Go to the next step.
4 | INSPECT PCM CONNECTOR CONDITION • Disconnect the PCM connector. • Inspect for poor connection (such as damaged/pulled-out pins, corrosion). • Is there any malfunction? | Yes | Repair or replace the connector and/or terminals, then go to Step 8.
No | Go to the next step.
5 | INSPECT CHT SENSOR CONTROL CIRCUIT FOR SHORT TO POWER SUPPLY • CHT sensor and PCM connectors are disconnected. • Turn the ignition switch to the ON position (engine off). • Measure the voltage at the CHT sensor terminal A (wiring harness-side). • Is there any voltage? | Yes | Repair or replace the wiring harness for a possible short to power supply, then go to Step 8.
No | Go to the next step.
6 | INSPECT CHT SENSOR CIRCUIT FOR OPEN CIRCUIT • CHT sensor and PCM connectors are disconnected. • Turn the ignition switch off. • Inspect for continuity between the following terminals (wiring harness-side): ― CHT sensor terminal A—PCM terminal 2AV ― CHT sensor terminal B—PCM terminal 2G • Is there continuity? | Yes | Go to the next step.
No | Repair or replace the wiring harness for a possible open circuit, then go to Step 8.
7 | INSPECT CHT SENSOR • Inspect the CHT sensor. (See CYLINDER HEAD TEMPERATURE (CHT) SENSOR INSPECTION [MZI-3.7].) • Is there any malfunction? | Yes | Replace the CHT sensor, then go to the next step. (See CYLINDER HEAD TEMPERATURE (CHT) SENSOR REMOVAL/INSTALLATION [MZI-3.7].)
No | Go to the next step.
8 | VERIFY DTC TROUBLESHOOTING COMPLETED • Make sure to reconnect all disconnected connectors. • Clear the DTC from the PCM memory using the M-MDS. (See AFTER REPAIR PROCEDURE [MZI-3.7].) • Retrieve the DTCs using the M-MDS. (See ON-BOARD DIAGNOSTIC TEST [MZI-3.7].) • Is the same DTC present? | Yes | Repeat the inspection from Step 1. • If the malfunction recurs, replace the PCM. (See PCM REMOVAL/INSTALLATION [MZI-3.7].) Go to the next step.
No | Go to the next step.
9 | VERIFY AFTER REPAIR PROCEDURE • Perform the “AFTER REPAIR PROCEDURE”. (See AFTER REPAIR PROCEDURE [MZI-3.7].) • Are any DTCs present? | Yes | Go to the applicable DTC inspection. (See DTC TABLE [MZI-3.7].)
No | Troubleshooting completed.