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DTC P1391 [MZR-CD (RF Turbo)]

id0102f1837100

DTC P1391 | Glow plug circuit low input
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DETECTION CONDITION | • The PCM monitors the output signal to the glow plug relay when the glow relay is on. If the glow relay voltage is 0.25 V or less when the glow relay is operating, The PCM determines that there is a malfunction in the glow relay circuit.
POSSIBLE CAUSE | • Glow plug relay malfunction • Melt or burnt glow fuse • PCM malfunction • Glow plug malfunction • Connector or terminal malfunction • Open circuit in wiring harness between glow plug relay terminal A and PCM terminal 75 • Open circuit in wiring harness between glow plug relay terminal C and PCM terminal 37 • Open circuit in wiring harness between glow plug relay terminal B and body ground • Open circuit in wiring harness between glow plug relay terminal D and GLOW FUSE • Short to ground circuit in wiring harness between glow plug relay terminal A and PCM terminal 75 • Short to ground circuit in wiring harness between glow plug relay terminal C and PCM terminal 37

Diagnostic procedure

STEP | INSPECTION | ACTION
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1 | VERIFY FREEZE FRAME DATA HAS BEEN RECORDED • Has FREEZE FRAME DATA been recorded? | Yes | Go to the next step.
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 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 | VERIFY CURRENT SIGNAL STATUS: IS CONCERN INTERMITTENT OR CONSTANT? • Connect the WDS or equivalent to the DLC-2. • Clear the DTC from the PCM memory using the WDS or equivalent. • Start the engine. • Is the same DTC present? | Yes | Go to the next step.
No | Intermittent concern exists. Perform the "INTERMITTENT CONCERN TROUBLESHOOTING". (See INTERMITTENT CONCERN TROUBLESHOOTING [MZR-CD (RF Turbo)].)
4 | FUEL INJECTOR CONNECTOR FOR POOR CONNECTION • Turn the engine switch to the ON position. • Inspect for poor connection (such as damaged/pulled- out terminals, corrosion). • Is there any malfunction? | Yes | Repair or replace the terminal, then go to Step 14.
No | Go to the next step.
5 | INSPECT GLOW PLUG RELAY CONNECTOR FOR POOR CONNECTION • Turn the engine switch off. • Disconnect the glow plug relay 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 the next step.
No | Go to the next step.
6 | INSPECT GLOW PLUG RELAY POWER SUPPLY FOR OPEN CIRCUIT • Turn the engine switch off. • Measure the voltage between glow plug relay terminal D and body ground. • Is the voltage B+? | Yes | Go to the next step.
No | Repair or replace the wiring harness for an open circuit, go to Step 14.
7 | INSPECT GLOW PLUG RELAY GROUND FOR OPEN CIRCUIT • Turn the engine switch off. • Remove the glow plug relay. • Inspect for continuity between glow plug relay terminal B and ground. • Is there continuity? | Yes | Go to the next step.
No | Repair or replace the wiring harness for an open circuit, go to Step 14.
8 | INSPECT GLOW PLUG RELAY SIGNAL FOR OPEN CIRCUIT • Turn the engine switch to the ON position (Engine off). • Measure the voltage between glow plug relay terminal C. • Is voltage less than 0.25 V? | Yes | Repair or replace the wiring harness for an open circuit, go to Step 14.
No | Go to the next step.
9 | INSPECT GLOW PLUG RELAY SIGNAL CIRCUIT FOR SHORT TO GROUND • Turn the engine switch off. • Inspect for continuity between glow plug relay terminal C and body ground. • Is there continuity? | Yes | Repair or replace the wiring harness for a short to ground, go to Step 14.
No | Go to the next step.
10 | INSPECT GLOW PLUG RELAY • Inspect the glow plug relay. (See RELAY INSPECTION.) • Is there any malfunction? | Yes | Go to the next step.
No | Replace the glow plug relay, go to Step 14.
11 | INSPECT POOR CONNECTION OF PCM CONNECTOR • Turn the engine switch off. • Inspect for poor connection (such as damaged/pulled-out terminals, corrosion). • Is there any malfunction? | Yes | Repair or replace the suspected terminal, go to Step 14.
No | Go to the next step.
12 | INSPECT GLOW PLUG RELAY SIGNAL CIRCUIT FOR SHORT TO GROUND • Turn the engine switch off. • Remove the glow plug connector. • Inspect for continuity between glow plug relay terminal A and body ground. • Is there continuity? | Yes | Repair or replace the wiring harness for a short to ground, then go to Step 14.
No | Go to the next step
13 | INSPECT GLOW PLUG RELAY SIGNAL CIRCUIT FOR OPEN CIRCUIT • Turn the engine switch off. • Inspect for continuity between glow plug relay terminal A and PCM terminal 75. • Is there continuity? | Yes | Go to the next step
No | Repair or replace the wiring harness for an open circuit, then go to the next step.
14 | VERIFY TROUBLESHOOTING OF DTC P1391 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, go to the next step. (See PCM REMOVAL/INSTALLATION [MZR-CD (RF Turbo)].)
No | Go to the next step.
15 | VERIFY AFTER REPAIR PROCEDURE • Perform the Repair Verification Drive Mode. (See OBD DRIVE MODE [MZR-CD (RF Turbo)].) • Are any DTCs present? | Yes | Go to the applicable DTC inspection. (See DTC TABLE [MZR-CD (RF Turbo)].)
No | Troubleshooting completed.