This 13-page PDF is a CAT C15 DTC 0105-03 troubleshooting procedure covering the intake manifold air temperature voltage high condition on C15 on-highway truck engines (MXS, NKS, RKS prefixes). The document details the conditions that generate code 0105-03, the ECM system response, and a complete seven-step diagnostic sequence from connector inspection through ECM replacement.
Official CAT C15 DTC 0105-03 document details
| Brand | Caterpillar (CAT) |
| Model coverage | C15 Truck Engine MXS (MXS00001-UP), also applicable to NKS and RKS configurations |
| System / Group | Engine Temperature Sensors — Diagnostic Trouble Codes (SMCS 1439-038-AI; 1921-038) |
| Publication no. | RENR5088-10 |
| Year / Revision | Published 01/02/2009, updated 25/02/2009 |
| Pages | 13 |
| File size | 0.3 MB |
| Format | |
| Language | English |
Document table of contents
- 0105-03 Intake Manifold Air Temperature Voltage High (38) — Conditions Which Generate This Code
- System Response — ECM default behavior, cooling fan activation, extreme cold mode suppression
- Engine Temperature Sensor Open or Short Circuit — Test (covers codes 105-03, 105-04, 110-03, 110-04, 171-03, 171-04, 174-03, 174-04)
- Pull-up Voltage explanation and schematics (Illustrations 1–5)
- P1 and P2 ECM connector pin assignments
- Test Step 1 — Inspect Electrical Connectors and Wiring (45 N pull test, torque check 6.0 N·m)
- Test Step 2 — Check for Active Diagnostic Codes using Caterpillar Electronic Technician (Cat ET)
- Test Step 3 — Disconnect Suspect Sensor to Create an Open Circuit
- Test Step 4 — Check Pull-up Voltage at Sensor Connector (5.5 ± 0.5 VDC)
- Test Step 5 — Check Signal Wire for a Short Circuit (resistance greater than 20,000 Ohms)
- Test Step 6 — Create a Short at the Suspect Sensor Connector with jumper wire
- Test Step 7 — Check ECM Operation; replace ECM if required
Applicable truck models
This procedure applies to Caterpillar C15 on-highway truck engines with serial prefix MXS (MXS00001-UP). The same diagnostic steps also cover NKS and RKS prefix C15 engines. The guide addresses the intake manifold air temperature sensor, coolant temperature sensor, ambient air temperature sensor, and fuel temperature sensor — all sharing identical troubleshooting logic. Sensor locations and ECM connector pinouts (P1 and P2) are illustrated for each sensor. For additional product support, visit Caterpillar Official Support.
Who needs this CAT C15 DTC 0105-03 manual
Diesel mechanics and workshop owners working on C15-powered trucks will need this guide whenever the ECM logs code 0105-03 with the check engine lamp illuminated. It provides the exact voltage thresholds, pin locations, and pass/fail criteria required to isolate the fault to the sensor, harness, or ECM without unnecessary part replacement.
The full PDF is available in the DiagTechPro manuals library, free account required to download.
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