Cummins fault code 191 is a diagnostic troubleshooting document for the ISB CM550 air conditioner clutch supply circuit. It explains how the ECM controls the air conditioner clutch solenoid and gives resistance, connector, harness, and verification checks for this fault. The PDF is useful when the A/C clutch circuit has damaged pins, open circuits, shorts to ground, or excessive current draw.
Official Cummins fault code 191 document details
| Brand | Cummins |
|---|---|
| Model coverage | ISB CM550 (1990-94) |
| System/Group | DTCs; Air Conditioner Clutch Supply Circuit |
| Year/Revision | Unknown |
| Pages | 5 |
| File size | 0.5 MB |
| Format | |
| Language | English |
Document table of contents
- FAULT CODE: 191
- PID: P050
- SPN: 876
- FMI: 11
- AIR CONDITIONER CLUTCH SUPPLY CIRCUIT
- Description
- Component location
- Troubleshooting steps
- Step 1A: Air conditioner clutch or relay inspection and current draw check
- Step 2A: Engine harness and ECM connector inspection
- Step 2B: Open circuit test from pin 21 to pin J
- Step 2C: Short circuit to ground test
- Step 2D: Short circuit between pins test
- Step 3A: OEM harness and 23-pin connector inspection
- Step 3B: OEM harness open circuit test
- Step 3C: OEM harness short circuit to ground test
- Step 3D: OEM harness pin-to-pin short circuit test
- Step 4A: Disable fault code and verify inactive status
- Step 4B: Clear inactive fault codes
Applicable truck models
This file applies to Cummins ISB CM550 (1990-94) coverage in the DTC group. The extract does not identify a specific truck chassis; it directs technicians to the original equipment manufacturer diagram for the air conditioner clutch solenoid location and uses OEM harness and 23-pin connector checks in the procedure. For manufacturer information, visit Cummins official website.
Who needs this Cummins fault code 191 manual
Workshop owners, diesel mechanics, and electrical diagnostic technicians need this manual when diagnosing the air conditioner clutch supply circuit on ISB CM550 applications. It supports checks for damaged pins, corroded pins, moisture, missing seals, open circuits, shorts to ground, shorts between pins, and final fault-code clearing with a diagnostic tool.
The full PDF is available in the DiagTechPro manuals library, free account required to download.
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