This document is a CAT C15 high battery troubleshooting guide for diagnostic code 0168-03 (High ECU Battery Power) on Caterpillar C15 on-highway truck engines (MXS configuration). It provides step-by-step test procedures covering the ignition keyswitch circuit, battery supply circuit, ECM connector inspection, voltage measurement, battery load testing, and bypass harness installation to isolate intermittent power faults.
Official CAT C15 high battery troubleshooting document details
| Brand | Caterpillar (CAT) |
| Model coverage | C15 Truck Engine MXS (MXS00001-UP) |
| System / Group | C15 DTCs — SMCS 1401-038; 1553-038 |
| Publication no. | RENR5088-10 |
| Year / Revision | Published 01/02/2009, Updated 25/02/2009 |
| Pages | 10 |
| File size | 0.3 MB |
| Format | |
| Language | English |
Document table of contents
- 0168-03 High ECU Battery Power — Conditions Which Generate This Code, System Response
- Ignition Keyswitch Circuit and Battery Supply Circuit — Test (System Operation Description)
- Schematic for ECM Battery Circuit (Illustration 1)
- Test Step 1: Inspect the Electrical Connectors and the Wiring (J1/P1 ECM connector, terminal locations P1-48, P1-52, P1-53, P1-63, P1-65, P1-67, P1-70)
- Test Step 2: Use Cat ET to Check for Communications with the ECM
- Test Step 3: Check for Active Diagnostic Codes or Logged Diagnostic Codes (43-2, 168-0, 168-1, 168-2)
- Test Step 4: Check for Battery Voltage at the ECM Connector (12V and 24V expected ranges)
- Test Step 5: Check the Batteries (load test using 4C-4911 Battery Load Tester, SEHS9249, SEHS7633)
- Test Step 6: Bypass Harness Procedure (167-9225 Harness, isolating intermittent vehicle wiring faults)
Applicable truck models
This procedure applies to Caterpillar C15 on-highway truck engines in the MXS configuration (serial prefix MXS00001-UP). It covers both 12-volt and 24-volt electrical systems. The document references the “Vehicle Voltage Selection” ECM parameter that determines battery voltage thresholds — 16.0 VDC for 12-volt systems and 32.0 VDC for 24-volt systems. Vehicles equipped with aftermarket engine protection shutdown systems or idle timer shutdown systems that interrupt keyswitch power are also addressed. For official Caterpillar parts and service resources, visit Caterpillar Support.
Who needs this CAT C15 high battery troubleshooting manual
Diesel mechanics and workshop owners diagnosing DTC 0168-03 on C15 engines need this reference. It is essential for anyone encountering engine derate with the check engine lamp illuminated due to excessive ECM battery voltage, or investigating related codes such as 168-2 and 43-2 keyswitch faults.
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