This PACCAR CAN troubleshooting procedure is the definitive step-by-step guide for diagnosing U-code and CAN network faults on PACCAR MX EPA diesel engines. Published by PACCAR and extracted from their technical support portal, it covers complete electrical isolation, voltage and resistance testing, and termination resistor diagnostics across three independent CAN networks (V-CAN, E-CAN, and A-CAN) used in EPA 2004 and EPA 2013 compliant powerplants.
Intended for technicians using DAVIE diagnostic software and PACCAR service manuals, this resource walks through visual inspections, power supply verification, and network resistance measurements at critical test points including the 9-pin diagnosis connector, PCI ECU (D420), EAS-3 ECU (D374), VTG turbo actuator (L037), and aftertreatment sensors.
Document details and specifications — PACCAR CAN troubleshooting
| Brand | PACCAR |
| System / Group | DTCs / MX Europe Engines (EPA 2004) |
| Publication No. | U1565B |
| Pages | 7 |
| File size | 0.1 MB |
| Format | |
| Language | English |
| Revision date | 18 August 2017 |
Table of contents
- General troubleshooting – CAN (MX_EPA13, MX_EPA04)
- Step 1: Investigate related DTCs (1A, 1B)
- Step 2: CAN-related component and power checks (2A, 2B)
- Step 3: Isolate faulty CAN network or component (3A, 3B, 3C, 3D)
- Step 3A: Electrical checks, resistance, V-CAN network
- Step 3B: Electrical checks, resistance, V-CAN termination resistors
- Step 3C: Electrical checks, resistance, E-CAN termination resistors
- Step 3D: Electrical checks, resistance, A-CAN termination resistors
- Step 4: Clear CAN-related DTCs (4A)
Applies to these models
This troubleshooting guide applies to PACCAR MX series diesel engines with EPA 2004 and EPA 2013 emissions compliance, including all integrated CAN bus architectures. It covers the PCI (Powertrain Control Interface) ECU, EAS-3 (Electronic Air Spring) ECU, and all factory CAN-connected components. For OEM-specific connector pin locations and vehicle wiring diagrams, refer to PACCAR Rapido technical portal or contact PACCAR engine support. PACCAR official site
Who needs this PACCAR CAN troubleshooting procedure guide
Master technicians, diagnostic specialists, and workshop owners servicing PACCAR MX-powered trucks need this PACCAR CAN troubleshooting procedure to isolate network faults, verify electrical integrity, and clear U-code DTCs without causing secondary failures. It is essential for shops using DAVIE diagnostics and managing EPA 2004/2013 engine service.
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