PACCAR MX P104C is the diagnostic trouble code documented on this 9 pages extract from the 2013 PACCAR MX Diagnostic Service Manual, published by PACCAR for EPA2013 MX engines. PACCAR prints the fault as “Boost pressure – Data valid but too low”, in the manual’s standard fault code layout.
Document details for PACCAR MX P104C
| Brand | PACCAR |
|---|---|
| Model coverage | PACCAR MX engines, EPA2013 emissions level |
| System / group | DTCs / MX Engines (EPA2013) |
| Source publication | 2013 PACCAR MX Diagnostic Service Manual |
| Fault code | P104C — Boost pressure – Data valid but too low |
| Pages | 9 |
| File size | 0.7 MB |
| Format | |
| Language | English |
Fault code summary and monitor data
The manual lists 2 trip MIL with 3 drive cycle recovery, no readiness group and a crankcase freeze frame type. The diagnostic runs at steady load, above 50 C coolant and between minus 15 and 40 C ambient.
- Code number
- Fault code description
- Fault code information
- Description of component(s)
- Set condition of fault code
- Reset condition of fault code
- Possible causes
- Diagnostic Step-by-Step
- Verification Drive Cycle
Component and system background
Boost pressure is measured in the inlet manifold near cylinder 1 by sensor F802, and the reading drives the smoke limit, the soot and NOx emission calculations, the exhaust gas mass flow used for DEF dosing estimation by the EAS-3 system, and the calculated temperatures after the compressor and before the turbine.
Set and reset conditions for PACCAR MX P104C
The code is set when the PCI ECU (D420) detects that the measured boost pressure is more than 0.5 bar (7.3 psi) lower than the expected boost pressure for more than 50 seconds, and it clears when the fault is no longer detected. Listed causes are a leaking inlet air system, boost pressure sensor deviation and turbocharger failure. The procedure repeats the manual shop rule that the ignition must always be OFF when connecting or disconnecting electrical components, and that a breakout harness is used rather than back probing.
Applies to EPA2013 MX engines
The PACCAR MX P104C entry sits in the DTCs / MX Engines (EPA2013) section, so it applies to PACCAR MX engines built to that emissions level. Manufacturer product information is published on the PACCAR corporate website.
Who needs the PACCAR MX P104C fault code page
Technicians reading a live code, foremen writing an estimate and fleet managers deciding whether a truck stays in service all need the manufacturer wording rather than a generic code list.
The full PDF for MX P104C is in the DiagTechPro manuals library; a free account is required to download it.
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