This Cummins coolant sensor DTCs document explains Fault Code 422 for the coolant level sensor circuit on Cummins ISB CM550 applications. It identifies PID P111, SPN 111, FMI 2, describes the sensor function, and gives step-by-step circuit checks for the harness, connectors, ECM pins, and final fault-code clearing.
Official Cummins coolant sensor DTCs document details
| Brand | Cummins |
|---|---|
| Model coverage | ISB CM550 (1990-94) |
| System/Group | DTCs; Coolant Level Sensor Circuit |
| Publication no. | Not stated |
| Year/Revision | Unknown; Copywrite 2017 shown in file |
| Pages | 6 |
| File size | 0.5 MB |
| Format | |
| Language | English |
Document table of contents
- FAULT CODE: 422
- PID: P111
- SPN: 111
- FMI: 2
- COOLANT LEVEL SENSOR CIRCUIT
- DESCRIPTION
- COMPONENT LOCATION
- TROUBLESHOOTING STEPS
- Step 1A: Turn key switch ON and read fault codes using the diagnostic tool
- Step 1B: Check whether the vehicle has a coolant level sensor
- Step 2A: Inspect the coolant level sensor and jumper harness connector pins
- Step 2B: Check for an open circuit
- Step 2C: Check for a short circuit to ground
- Step 2D: Check for a short circuit from pin to pin
- Step 3A: Inspect the engine harness and the ECM connector pins
- Step 3B: Check for an open circuit between ECM connector pins and sensor jumper harness pins
- Step 3C: Check for a short circuit to ground in the coolant level sensor signal wires
- Step 3D: Check for a short circuit from pin to pin
- Step 4A: Disable the fault code and verify Fault Code 422 is inactive
- Step 4B: Clear inactive fault codes
Applicable truck models
This file covers Cummins ISB CM550 engines listed under the 1990-94 group. The extract also notes OEM variation in coolant level sensor location, with the sensor located in the radiator top tank or surge tank, and mentions Sterling trucks using ECM pin A22 for coolant level sensing through a 2-pin sensor. The procedure applies to vehicles with a coolant level sensor or a correctly installed shorting plug in place of the sensor harness connection. For manufacturer information, see the official Cummins website.
Who needs this Cummins coolant sensor DTCs manual
Mechanics, fleet technicians, and workshop owners need this manual when diagnosing Fault Code 422, SPN 111 FMI 2, on ISB CM550 engines. It is useful when checking coolant level sensor connectors, Weather-Pack four-way connector wiring, jumper harness continuity, shorts to ground, ECM connector pins, and final confirmation with a diagnostic tool.
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