Cummins M11 code 343 is the Cummins troubleshooting document for the Fault Processing Computer (FPC) Chip fault (PID S254, SPN 629, FMI 12, SRT 00-606). The ECM is the computer responsible for engine control, diagnostics, and user features, and this procedure addresses a fault reported by the fault processing computer (FPC) chip inside the ECM. It sets a yellow warning lamp and lists the exact conditions, causes, and step-by-step checks a technician follows.
Official document details
| Brand | Cummins |
|---|---|
| Model coverage | Cummins M11 CELECT electronic engines built 1990 to 1994 |
| System / Group | M11 CELECT (1990-94) |
| Fault identifiers | PID S254, SPN 629, FMI 12, SRT 00-606 |
| Warning lamp | Yellow |
| Pages | 5 |
| Format | |
| Language | English |
Document table of contents
- Circuit description
- Component location
- Shop Talk
- Step-by-step troubleshooting steps
- Fault code clearing and verification
Trucks covered by Cummins M11 code 343
This procedure applies to Cummins M11 CELECT electronic engines built 1990 to 1994. The procedure carries the Cummins fault identifiers PID S254, SPN 629, FMI 12, SRT 00-606 for reference and repair-time tracking. It is set by loose engine or chassis ground connections, moisture in the ECM connectors, a damaged engine position sensor, a defective alternator, or intermittent shorts to ground, and typical effects include possible intermittent engine stumble, and related codes such as 121 and 115 being logged. For engine specifications and dealer support, see the official Cummins website.
Who needs this Cummins M11 code 343 manual
Heavy-truck technicians, fleet maintenance teams, and workshop owners diagnosing this fault use it to confirm the code before replacing parts. During diagnosis special attention is paid to the negative starter post connection, and running the engine with the alternator belt off can reveal a defective alternator. The step-by-step tree starts by reading active and inactive codes with the diagnostic tool, then inspects the harness and connector pins for bent, corroded, pushed-back, or expanded pins, flushing them with electronic contact cleaner Part Number 3824510 before any component is condemned. Test leads run around the bulkhead are used to isolate a faulty OEM harness, and the code is rechecked and cleared once the repair passes.
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Applies to these truck models
This is the manufacturer document shared across 2 model families. It applies to:
- Cummins DTCs
- Cummins M11 CELECT (1990-94)
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