PACCAR MX P0127 is the fault code page for “Intercooler temperature – Data valid but too high, most severe” 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
Intercooler outlet temperature is measured by sensor F750 before the EGR mixer, and its job is to monitor intercooler performance. The data is valid here, which is the point: the sensor is telling the truth and the charge air really is too hot.
Set and reset conditions
The diagnostic starts 300 seconds after the engine is started. It sets when the PCI ECU D420 sees intercooler outlet temperature above 100 C for more than 30 seconds. Engine torque is reduced while the code is active.
PACCAR MX P0127 wiring and technical data
The sensor has a signal and a ground circuit into connector D420.C, with resistance values for checking it cold. The fault code information block records it as 1 trip MIL, 3 drive cycle recovery, readiness group none, freeze frame type Boost.
| D420 pin | F750 pin | Function |
|---|---|---|
| C17 | 1 | Signal, intercooler temperature |
| C31 | 2 | Ground |
| – | 1 to 2 | 2334 to 2505 ohm at 20 C |
Possible causes and working notes
- Contaminated intercooler
- Faulty engine cooling fan
- Intercooler temperature sensor deviation
- Use of a winterfront above 4 C
- Aftermarket winterfront restricting airflow
The validation drive is spelled out: warm the coolant to at least 70 C, then make several low to higher speed accelerations under moderate load plus high-load to low-load transitions, between 15 and 65 km/h for no more than 5 to 8 km.
Document details and format
| Field | Value |
|---|---|
| Brand | PACCAR |
| System group | DTCs, MX Engines (EPA2013) |
| Source publication | 2013 PACCAR MX Diagnostic Service Manual |
| Manual page | 145 |
| Pages | 9 |
| File size | 0.6 MB |
| Format | PDF, English |
Applies to PACCAR MX P0127 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 P0127 page
Technicians chasing heat-related derates on a PACCAR MX engine, especially trucks running a winterfront in mild weather.
The full PDF page is in the DiagTechPro manuals library; a free account downloads it. Keep the PACCAR MX P0127 sheet open next to DAVIE.
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