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Unswitched Battery Supply Circuit
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Overview
| CODE | REASON | EFFECT |
| Fault Code: 441 PID: S168 SPN: 168 FMI: 1/18 LAMP: Yellow SRT: |
Voltage detected at electronic control module (ECM) power supply pins indicates low ECM supply voltage. |
Engine can die or run rough. |
 Unswitched Battery Supply
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Circuit Description
The electronic control module (ECM) receives constant voltage from the batteries through the unswitched battery wires that are connected directly to the positive (+) battery post. There is either one in-line 30-amp fuse or two in-line 15-amp fuses in the unswitched battery wires to protect the OEM harness from overheating. The ECM receives switched battery input through the vehicle keyswitch wire when the vehicle keyswitch is turned ON. The battery return wires are connected directly to the negative (-) battery post.
Component Location
The ECM is located on the left side of the engine. The ECM is connected to the battery by the OEM harness. This direct link provides a constant power supply for the ECM. The location of the battery will vary with the OEM. Use the OEM manual.
Shop Talk
- Verify that the ECM unswitched power is coming from the batteries and not the starter or other device. Check for possible weak batteries.
- If the ECM unswitched battery supply is taken from the starter, check for low voltage during cranking. Low voltage during cranking can cause the ECM power supply to drop below specifications and log Fault Code 441.
Refer to Troubleshooting Fault Code t05-441
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