This document is a Cummins ambient pressure sensor troubleshooting sheet for Fault Code 221 on ISB CM550 engines. It explains the ambient air pressure sensor circuit, component location, diagnostic-tool checks, connector inspections, voltage measurements, resistance tests, and repair verification steps.
Official Cummins ambient pressure sensor document details
| Brand | Cummins |
|---|---|
| Model coverage | ISB CM550 engines; 300 horsepower rated engines and specific 275 horsepower rated engines requiring the ambient air pressure sensor |
| System/Group | ISB CM550 (1990-94) / DTCs; Ambient Air Pressure Sensor Circuit |
| Publication no. | Not shown in extract |
| Year/Revision | Unknown |
| Pages | 5 |
| File size | 0.5 MB |
| Format | |
| Language | English |
Document table of contents
- Fault Code: 221
- PID: P108
- SPN: 108
- FMI: 3
- Ambient Air Pressure Sensor Circuit
- Description
- Component Location
- Troubleshooting Steps
- Step 1A: Turn key switch ON and read the fault codes using the diagnostic tool
- Step 2A: Disconnect the engine harness from the ambient air pressure sensor and inspect connector pins
- Step 2B: Check the ECM ambient air pressure supply voltage with breakout cable Part No. 3162899
- Step 2C: Check the ECM ambient air pressure signal voltage
- Step 3A: Inspect the engine harness and ECM connector pins
- Step 3B: Check for an open circuit in the ambient air pressure signal wire
- Step 3C: Check for a short circuit to ground
- Step 3D: Check for a short circuit from pin to pin
- Step 4A: Disable the fault code and verify that Fault Code 221 is inactive
- Step 4B: Clear the inactive fault codes using the diagnostic tool
Applicable truck models
This file applies to Cummins ISB CM550 engines in the 1990-94 DTC group where Fault Code 221 is active for the ambient air pressure sensor circuit. The extract states that the sensor is required with 300 horsepower rated engines and specific 275 horsepower rated engines, and that the sensor is located below the fuel transfer pump. For manufacturer information, see the Cummins official website.
Who needs this Cummins ambient pressure sensor manual
Mechanics, fleet technicians, and workshop owners need this Cummins ambient pressure sensor manual when diagnosing FMI 3, SPN 108, PID P108, or a high-voltage sensor circuit fault. The procedure helps confirm whether the cause is sensor failure, damaged connector pins, moisture, missing seals, an open signal wire, a short to ground, a pin-to-pin short, or an engine harness fault.
The checks use a diagnostic tool, key switch ON/OFF steps, breakout cable Part No. 3162899, and voltage or resistance measurements at the sensor, harness, chassis ground, and ECM connector pin 32. Listed limits include 4.5 to 5.25 VDC for supply voltage, altitude-based signal voltage ranges from sea level to 12000 ft, less than 10 ohms for continuity, and more than 100k ohms for short-circuit checks. After repairs, the procedure reconnects all components, disables the fault code, idles the engine for 1 minute, verifies Fault Code 221 is inactive, and clears inactive codes.
Full PDF available in the DiagTechPro manuals library, free account required to download.
Related manuals library
Sản phẩm liên quan cho hãng này
Cùng brand theo taxonomy hiện có trong catalog WooCommerce.
Cummins Calterm Version 5.16 – Advanced ECM Control and Precision Tuning for Cummins Engines
Cummins INSITE 9.3 – The Essential Diagnostic Tool for Cummins Engines
Cummins InCal CE – The Calibration and Configuration Tool for Cummins Engines
