This document is a C15 barometric pressure DTCs troubleshooting guide for DTC 0108-03 (Barometric Pressure voltage high), published by Caterpillar for the C15 On-Highway Truck Engine (MXS configuration). It provides step-by-step diagnostic procedures to identify and resolve high signal voltage conditions on the atmospheric pressure sensor circuit, including wiring inspections, supply voltage checks, and ECM verification tests.
Official C15 barometric pressure DTCs troubleshooting document details
| Brand | Caterpillar (CAT) |
| Model coverage | C15 Truck Engine MXS (MXS00001-UP) |
| System / Group | DTCs — Engine Pressure Sensors (SMCS 1439-038-AI; 1923-038) |
| 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
- 0108-03 Barometric Pressure Voltage High (26) — Conditions Which Generate This Code, System Response
- Engine Pressure Sensor Open or Short Circuit — Test (covers DTCs 100-3, 100-4, 102-3, 102-4, 108-3, 108-4, 385-3, 385-4)
- 108-3 Diagnostic Code and High Crankcase Pressure
- Schematic for Engine Pressure Sensors (Illustration 1)
- Locations of Engine Pressure Sensors — Boost, Barometric, Oil, Intake Valve Actuation (Illustrations 2–3)
- Terminal Locations at the P2 ECM Connector (Illustration 4)
- Terminal Locations at the Sensor Connector (Illustration 5)
- Test Step 1: Determine if the Code is Logged or Active
- Test Step 2: Check for Intermittent Problems at Connectors
- Test Step 3: Check the Supply Voltage at the Sensor Connector (4.5–5.5 VDC)
- Test Step 4: Check for Battery Voltage on the Signal Wire
- Test Step 5: Sensor Replacement Verification (jumper wire test)
- Test Step 6: Check the ECM for Proper Operation
- Test Step 7: Check the Signal Wire for a Short Circuit
- Test Step 8: ECM Open Circuit Detection and Wiring Repair
Applicable truck models
This troubleshooting procedure applies to the Caterpillar C15 On-Highway Truck Engine, configuration MXS00001-UP. The Engine Control Module (ECM) triggers DTC 0108-03 when the atmospheric pressure sensor signal exceeds 4.95 VDC for more than 30 seconds, causing a 10 percent power derate and a default atmospheric pressure reading of 100 kPa (15 psi). The document also addresses related pressure sensor codes for oil pressure (100-3/4), boost pressure (102-3/4), and intake valve actuation system oil pressure (385-3/4). The procedure identifies P2 ECM connector terminal locations including P2-57 for barometric pressure, P2-15 for boost, P2-28 for oil pressure, and P2-74 for intake valve actuation. For official Caterpillar parts and technical resources, visit Caterpillar Support.
Who needs this C15 barometric pressure DTCs troubleshooting manual
Diesel mechanics and workshop owners servicing C15-powered trucks with an active or logged 108-03 code will find this guide essential. It walks through every test step from connector wiggle tests and multimeter measurements to jumper-wire sensor substitution and test ECM installation, enabling systematic fault isolation without unnecessary part replacement.
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