P0606 means the module doubts the integrity of its own processor. Checks include a question-and-answer game between main and monitoring processor (GM: new seed via SPI within 450 ms; Ford: 'quizzer' level 3), arithmetic unit and register tests, stack overflow, the order in which safety-critical software runs, and the internal voltage supply (Ford diesel: 5 V rail outside 4.7–5.3 V). Because it belongs to the electronic throttle safety concept, the module usually reacts with a failure mode – reduced power, RPM limit or throttle default position – and the lamp in the first trip. Many cases are software issues fixed by reprogramming (Chrysler 3.6 L 2014, VW Routan, GM brake module 2024), so check bulletins before replacing hardware. The code alone does not say which module set it – the scan tool shows whether it is the engine, transmission, brake or body module.
High severity. Can I keep driving?Do not use it for trips: it can suddenly shut off or lock into limp mode with very little power. If it is in reduced-power mode or jerking, stop in a safe place and call a tow truck.
Symptoms
- Check engine light, at Ford also the wrench lamp
- Limp mode with reduced power or RPM limit
- Poor throttle response
- Rarely stalling or no start
- Often together with voltage codes P0562/P0563
Most likely causes
- Faulty module software (update available)
- Low voltage, voltage dips or a poor ground or supply at the module
- Internal hardware defect (processor, voltage regulator, output stage chip)
- Short on a 5 V sensor reference loading the internal supply
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: hard
- It can trigger limp mode.
- It affects emissions.
What each character of P0606 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 6: Control modules and outputs
- 06: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0606?
Do not use it for trips: it can suddenly shut off or lock into limp mode with very little power. If it is in reduced-power mode or jerking, stop in a safe place and call a tow truck.
What causes code P0606?
The most common causes are: faulty module software (update available); low voltage, voltage dips or a poor ground or supply at the module; internal hardware defect (processor, voltage regulator, output stage chip).
Related codes
- P0600Serial Communication Link
- P0607Control Module Performance
- P060AInternal Control Module Monitoring Processor Performance
- P060BInternal Control Module A/D Processing Performance
- P060CInternal Control Module Main Processor Performance
- P0562System Voltage Low
Sources
- law.cornell.edu: 13 CCR 1968.2
- gsi.ext.gm.com: 25OBDG03A
- fordservicecontent.com: OBD Operations Summary Gasoline 2020 2023
- fordservicecontent.com: obd summary diesel 2023
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.