This 18-page PDF is the official C15 coolant level DTCs troubleshooting procedure published by Caterpillar for the C15 On-Highway Truck Engine (MXS configuration). It provides step-by-step diagnostic instructions for fault code 0111-02 (Coolant Level Signal Invalid) and the complete Coolant Level Sensor Circuit Test used to resolve DTCs 111-2, 111-3, and 111-4.
Official C15 coolant level DTCs troubleshooting document details
| Brand | Caterpillar (CAT) |
| Model coverage | C15 Truck Engine MXS (MXS00001-UP) |
| System / Group | Engine Coolant Level Sensor Circuit — SMCS 1439-038-CLT |
| Publication no. | RENR5088-10 |
| Year / Revision | Published 01/02/2009, updated 25/02/2009 |
| Pages | 18 |
| File size | 0.3 MB |
| Format | |
| Language | English |
Document table of contents
- 0111-02 Coolant Level Signal Invalid (12) — Conditions Which Generate This Code, System Response
- Coolant Level Sensor Circuit — Test: System Operation Description
- 4-Pin Sensor wiring and voltage behavior (terminals P1-2, P1-54, P1-49, P1-5)
- 2-Wire Float Sensor wiring and voltage behavior (terminals P1-26, P1-5)
- Test Step 1: Check for Active Diagnostic Codes (111-2, 111-3, 111-4)
- Test Step 2–3: Inspect connectors, harness and wiring for corrosion, abrasion, pinch points
- Test Step 4: Check Supply Voltage at the Sensor (4.5–5.5 VDC)
- Test Step 5: Create a Short at the Sensor Connector
- Test Step 6–7: Check for Proper Operation of the ECM using jumper wires
- Test Step 8–10: 2-Wire Float Sensor connector inspection and pull test at P1 ECM connector
- Test Step 11: Check for Correct Voltage at the ECM Connector
- Test Step 12: ECM replacement procedure and final verification
Applicable truck models
This document applies to the Caterpillar C15 On-Highway Truck Engine in the MXS configuration (serial prefix MXS00001-UP). The procedures also reference NKS and RKS serial prefixes within the C15 DTC group. The coolant level sensor and its circuit are OEM-installed, meaning the exact harness routing varies by truck manufacturer. The ECM supports two sensor types: a 4-pin sensor using a +5 VDC supply on terminal P1-2 and a 2-wire float sensor using input No. 10 on terminal P1-26. The “Coolant Level Sensor” customer-programmable parameter must match the installed sensor type, or DTC 111-2 will be logged. Warning lamp behavior is controlled via the “Engine Monitoring Lamps” parameter, with a single lamp on P1-29 or a discrete low-coolant lamp on P1-30. For additional product support, visit Caterpillar’s official support page.
Who needs this C15 coolant level DTCs troubleshooting manual
Fleet mechanics and independent workshop technicians diagnosing an active or intermittent DTC 111-02 on a C15 MXS engine will find every required voltage test, connector pin-out, and ECM verification step in this document. It is also essential when reprogramming the coolant level sensor parameter after an OEM sensor swap.
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