Short answer: common signs of a failing ECM or PCM include no-start or stalling, no communication with a scan tool, a check engine light with module-related codes, erratic shifting, and problems that come and go with heat or moisture. Check power, grounds, wiring and connectors first. They cause many of the same symptoms and cost far less to fix.
Common symptoms
- Engine cranks but won’t start, or stalls for no clear reason
- Scan tool can’t communicate with the module
- Check engine light with internal control module codes (for example P0600–P0606)
- Rough running, misfires or poor fuel economy with no mechanical cause found
- Erratic or harsh shifting on vehicles where the PCM controls the transmission
- Problems that appear when hot, cold or wet and then go away
- Signs of water damage or corrosion on the module or its connector
What to check before replacing the module
- Battery and charging system: low voltage causes strange module behavior.
- Fuses and relays that power the module.
- Grounds: clean and tighten engine and module ground connections.
- Connectors and wiring: look for corrosion, bent pins and damaged wires.
- Software updates: some problems are fixed by a reflash rather than a new module.
If the module is bad
Note the part number on the original module and search for it. See How to find your module’s part number and Do I need to program a replacement module?
Frequently asked questions
Can a bad ECM damage other parts?
It can. A failing module can drive outputs incorrectly. It’s also common for a shorted sensor or wire to damage a module, so find and fix the cause before installing a replacement.
Find your module
Search the part number from your module’s label on Module Mountain, or shop by vehicle. Every module is refurbished to order, ships free by USPS Priority in the USA, and is covered by our one-year warranty (exchange and warranty policy). Can’t find your number? Email contact@modulemountain.com with a photo of the label and your VIN.