PACCAR MX P0118 is the fault code page for “Coolant Temperature – Voltage too high or short circuit to supply on ECU D420 pin A58” in the 2013 PACCAR MX Diagnostic Service Manual. PACCAR publishes it for engines in the EPA 2013 emissions family, and it is worked with the DAVIE diagnostic software.
What this fault code means
Coolant temperature sensor F566 is measured in the coolant return gallery at the right rear end of the cylinder block. The reading feeds injection quantity and timing, the driver display and high-temperature warnings, hot torque limiting, and the cold start aid.
Set and reset conditions
The code sets when the PCI detects sensor output voltage above 4.89 V, which is the classic signature of an open circuit or a signal wire shorted to supply. It goes inactive as soon as the diagnostic runs and passes.
PACCAR MX P0118 wiring and technical data
ECU D420 and sensor F566 are joined by a signal and a ground circuit, and the manual prints the resistance the sensor should show at each temperature step. The fault code information block records it as 1 trip MIL, 3 drive cycle recovery, readiness group none, freeze frame type Cooling.
| D420 pin | F566 pin | Function |
|---|---|---|
| A58 | 1 | Signal, coolant temperature |
| A61 | 2 | Ground |
| – | 1 to 2 | 5727 to 6056 ohm at 0 C |
Possible causes and working notes
- Faulty wiring
- Faulty connector
- Faulty sensor
Step 2 is a voltage check: key off, unplug the coolant temperature sensor, key on and measure between battery ground and the supply terminal of the sensor circuit on the engine harness. Back probing is discouraged; fit a breakout harness.
Document details and format
| Field | Value |
|---|---|
| Brand | PACCAR |
| System group | DTCs, MX Engines (EPA2013) |
| Source publication | 2013 PACCAR MX Diagnostic Service Manual |
| Manual page | 135 |
| Pages | 5 |
| File size | 0.5 MB |
| Format | PDF, English |
Applies to PACCAR MX P0118 repairs
The page sits in the DTCs section for MX engines built to the EPA 2013 emissions standard, so it covers trucks running that engine family with the PCI engine control unit. Coverage and dealer support are published on the PACCAR corporate site.
Who needs this PACCAR MX P0118 page
Technicians who need the exact high-voltage threshold and the harness measurement point when a coolant sensor circuit reads open on a PACCAR MX engine.
The full PDF page is in the DiagTechPro manuals library; a free account downloads it. Keep the PACCAR MX P0118 sheet open next to DAVIE.
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