This document provides diagnostic guidance for the CAN message out of range DTC U1878, a critical diagnostic trouble code affecting PACCAR MX Europe engines compliant with EPA 2004 and EPA 2013 emissions standards. Published by PACCAR and sourced from the official Rapido technical portal, this manual explains when and why this DTC is set, how to diagnose the root cause, and the correct repair verification procedure.
The U1878 code is triggered when a CAN (Controller Area Network) message is received by an ECU but the signal value or status contained within that message falls outside the expected operating range. This document is essential for understanding how CAN communication failures cascade across multiple electronic control units in PACCAR truck powertrains.
Document details and specifications — CAN message out
| Brand | PACCAR |
| Model coverage | MX EPA Engines (EPA 2004, EPA 2013) |
| System/Group | DTCs / MX Europe Engines |
| Publication number | U1878 |
| Year/Revision | 18 August 2017 |
| Pages | 2 |
| File size | 0.1 MB |
| Format | |
| Language | English |
Table of contents
- Set conditions — CAN message content validation
- Diagnostic condition — continuous monitoring when ignition on or engine running
- Corresponding OBD readiness monitor
- Reset condition — inactive after diagnostic passes
- Repair verification — 3-step test drive procedure
- Possible cause — corrupt or empty CAN messages, originating system malfunction
- Additional information — multi-ECU diagnostic examples and CAN communication principles
Applies to these models
This CAN message out of range DTC guide applies to PACCAR MX EPA diesel engines used in heavy-duty trucks compliant with EPA 2004 and EPA 2013 emissions regulations. The diagnostic methodology covers all CAN-networked ECUs within these powertrains. For official engine specifications and technical resources, visit PACCAR official website.
Who needs this CAN message out of range DTC manual
Diesel mechanics, heavy truck technicians, and workshop service managers working on PACCAR-powered vehicles require this message out of range DTC reference to correctly diagnose and repair CAN communication faults. The document explains how a fault in one system (such as a defective sensor) can trigger a ‘message out of range’ code in a different ECU, preventing unnecessary component replacement and reducing diagnostic time.
The complete message out of range DTC U1878 diagnostic manual is available in the DiagTechPro manuals library. A free account is required to download the full 2-page PDF.
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