This Cummins fault 386 document is a troubleshooting manual for the Sensor Supply Circuit on Cummins ISB CM550 engines. It explains the shared +5-VDC sensor supply, related sensor faults, harness checks, ECM connector inspection, and final repair verification steps.
Official Cummins fault 386 document details
| Brand | Cummins |
|---|---|
| Model coverage | ISB CM550 (1990-94) |
| System/Group | DTCs; Sensor Supply Circuit |
| Publication no. | Fault Code 386 |
| Year/Revision | Unknown; document copywrite 2017 shown in extract |
| Pages | 4 |
| File size | 0.3 MB |
| Format | |
| Language | English |
Document table of contents
- FAULT CODE: 386
- PID: S232
- SPN: 620
- FMI: 4 or 3
- SENSOR SUPPLY CIRCUIT
- DESCRIPTION
- COMPONENT LOCATION
- TROUBLESHOOTING STEPS
- Step 1A: Turn key switch ON and connect the diagnostic tool
- Step 1B: Disconnect the engine position sensor and check the engine position sensor
- Step 1C: Disconnect the intake manifold pressure sensor and check the intake manifold pressure sensor
- Step 1D: Disconnect the oil pressure sensor and check the oil pressure sensor
- Step 2A: Inspect the engine harness and the ECM connectors
- Step 2B: Check for a short circuit to ground in the engine harness
- Step 2C: Check for a short circuit from pin to pin
- Step 2D: Check for sensor +5-VDC supply voltage
- Step 3A: Verify that Fault Code 386 is inactive
- Step 3B: Clear the inactive fault codes using the diagnostic tool
Applicable truck models
This file applies to Cummins ISB CM550 (1990-94) engine diagnostics where Fault Code 386 is active or stored. The circuit described powers the engine position sensor, intake manifold pressure sensor, oil pressure sensor, intake manifold temperature sensor, and coolant temperature sensor from the same ECM +5-VDC source and return. It also notes that faults in this supply can cause high- or low-voltage faults on the coolant temperature and intake manifold temperature sensors. For current engine and service information, see the Cummins official website.
Who needs this Cummins fault 386 manual
Workshop technicians, fleet maintenance teams, and diagnostic tool users need this Cummins fault 386 manual when checking sensor supply voltage, harness shorts, damaged pins, connector moisture, or possible ECM replacement. It is useful when a repair must be verified by disabling the fault code, idling the engine, confirming Fault Code 386 is inactive, and clearing inactive codes.
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