This CAT C15 injector troubleshooting document provides the complete diagnostic procedure for resolving low and high injector current fault codes on Caterpillar C15 on-highway truck engines (MXS serial prefix). It details how the ECM detects open or short circuit conditions in the Electronic Unit Injector (EUI) solenoid circuits, the system responses triggered by these faults, and the step-by-step electrical tests required to isolate and repair the problem.
Official CAT C15 injector troubleshooting document details
| Brand | Caterpillar (CAT) |
| Model coverage | C15 Truck Engine MXS (C15 On-Highway Truck MXS00001-UP) |
| System / Group | Injector Solenoid Circuit — SMCS 1290-038 |
| Publication no. | RENR5088-10 |
| Year / Revision | Published 01/02/2009, updated 25/02/2009 |
| Pages | 17 |
| File size | 0.3 MB |
| Format | |
| Language | English |
Document table of contents
- 0001-05 Cylinder #1 Injector Current Low (72) — Conditions, System Response
- Injector Solenoid Circuit — Test (System Operation Description)
- Diagnostic codes covered: Cylinders 1–6, current low (x-05) and current high (x-06)
- Cylinder Cutout Test procedure (4-cylinder and manual modes)
- Injector Solenoid Test procedure (open/short detection with Cat ET)
- Test Step 1: Inspect Electrical Connectors and Wiring
- Test Step 3: Check the Variation of the Injectors between Cylinders
- Test Step 5: Check the Harness between ECM and Valve Cover Base for an Open Circuit
- Test Step 7: Check the ECM for an Open Circuit (using 257-8718 Adapter Cable / 120-PIN Breakout)
- Test Step 8: Check for a Short Circuit at P2 ECM Connector
- Resistance measurement procedures — return line short diagnosis
- Illustrations: Electronic Unit Injector, C15 engine schematic, P2 ECM connector pinout, valve cover connectors, injector harness connector
Applicable truck models
This publication applies exclusively to Caterpillar C15 on-highway truck engines with the MXS serial number prefix (MXS00001 and up). These engines use mechanically actuated, electronically controlled Electronic Unit Injectors (EUI) driven by a 105-volt pulse from the ECM. The P2 ECM connector pinout references pins P2-99, P2-104, P2-105, P2-106, P2-107, P2-108, P2-115, P2-116, and P2-118 for injector supply and return circuits. The document warns of a 90–120 volt electrical shock hazard present in the injector system. For official Caterpillar parts lookup and additional technical resources, visit Caterpillar Support.
Who needs this CAT C15 injector troubleshooting manual
Diesel mechanics and workshop owners diagnosing engine misfires, low power, or injector-related DTCs on CAT C15 MXS engines need this manual. It is essential for anyone using Caterpillar Electronic Technician (Cat ET) to perform Injector Solenoid Tests, Cylinder Cutout Tests, or harness continuity checks on these engines.
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