This document is the 2013 PACCAR MX Diagnostic Service Manual covering PACCAR MX engine fault, specifically the P0666 code for internal ECU temperature sensor diagnostics. Published by PACCAR for their MX engine line under EPA 2013 emission standards, it provides mechanics and technicians with comprehensive fault identification, diagnostic conditions, and step-by-step troubleshooting procedures for temperature-related electronic control unit (ECU) faults.
The manual explains how PACCAR MX engines monitor internal ECU health using integrated temperature sensors and atmospheric pressure sensors within the PCI ECU (D420), and outlines the exact conditions under which fault codes are triggered and cleared.
Document details and specifications — PACCAR MX engine
| Brand | PACCAR |
| Model coverage | MX Engine series |
| System/Group | DTCs / MX Engines (EPA 2013) |
| Publication number | Not specified in manual header |
| Year/Revision | 2013 |
| Pages | 4 (pages 15–18) |
| File size | 0.6 MB |
| Format | |
| Language | English |
Table of contents
- P0666 code number and fault description
- Fault code information (MIL trip, drive cycle recovery, freeze frame type)
- Component description: PCI ECU (D420), atmospheric pressure sensor, temperature sensor
- System effects on engine torque and ECU monitoring
- Injector calibration codes and DAVIE programming requirements
- Diagnostic conditions and fault set/reset logic
- Possible causes and additional diagnostic information
- Step-by-step troubleshooting procedures (Visual inspection, electrical checks, ECU replacement, PACCAR support contact)
- Verification drive cycle procedure
Applies to these models
This PACCAR MX engine fault manual applies to PACCAR MX series truck engines manufactured under the 2013 EPA emission standards. The P0666 internal ECU temperature diagnostic procedure covers all trucks equipped with the PCI ECU (D420) controller. For technical support and engine specifications, visit the PACCAR official website.
Who needs this PACCAR MX engine fault manual
Diesel truck mechanics, workshop owners, and technicians diagnosing P0666 faults or performing preventive ECU maintenance on PACCAR MX-powered trucks need this MX engine fault guide. Technicians using DAVIE diagnostic software or conducting 8-hour ignition-off diagnostics will rely on the precise conditions and electrical checks outlined here.
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