PACCAR MX P0115 is the fault code page for “Coolant temperature – Data erratic, intermittent, or incorrect at ignition on” 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 is measured in the coolant return gallery at the right rear end of the cylinder block. The manual lists what depends on it: injected fuel quantity and timing, the driver display and high-temperature warnings, torque limiting when coolant runs hot, and the cold start aid.
Set and reset conditions
This is an 8-hour soak diagnostic. It runs only after the ignition has been off at least 8 hours, with the coolant to ambient difference under 15 C and ambient above -20 C. It sets when the PCI ECU D420 finds the coolant reading differs by more than 3 C from the average of the other engine temperature sensors.
PACCAR MX P0115 wiring and technical data
The signal and ground pins are given for ECU D420, with a full resistance versus temperature table for the sensor. The fault code information block records it as 2 trip MIL, 3 drive cycle recovery, readiness group none, freeze frame type Cooling.
| D420 pin | Sensor pin | Function |
|---|---|---|
| A58 | 1 | Signal, coolant temperature |
| A61 | 2 | Ground |
| – | 1 to 2 | 2439 to 2557 ohm at 20 C |
Possible causes and working notes
- Engine block heater used
- Coolant temperature sensor deviation
To reset the check the truck must sit 8 to 10 consecutive hours, then be keyed on without starting for 10 seconds, then idled for 2 minutes.
Document details and format
| Field | Value |
|---|---|
| Brand | PACCAR |
| System group | DTCs, MX Engines (EPA2013) |
| Source publication | 2013 PACCAR MX Diagnostic Service Manual |
| Manual page | 126 |
| Pages | 4 |
| File size | 0.4 MB |
| Format | PDF, English |
Applies to PACCAR MX P0115 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 P0115 page
Shops that cannot reproduce a coolant temperature complaint on a PACCAR MX engine, where the check only runs after an overnight soak.
The full PDF page is in the DiagTechPro manuals library; a free account downloads it. Keep the PACCAR MX P0115 sheet open next to DAVIE.
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