P0606 Code: Meaning, Causes and Repair Cost

A control module, usually the engine computer, has found a problem with its own processor. Because it can no longer fully trust itself, it often limits power or engine speed as a safety measure. Many cases come from software that an update fixes, or from low voltage or a poor ground at the module, not from a dead computer.

How the engine computer detects it

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.

Written from public technical sources and not yet checked by a mechanic. How we write these pages

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

Common causes

Faulty module software (update available) Most likely
Low voltage, voltage dips or a poor ground or supply at the module Possible
Internal hardware defect (processor, voltage regulator, output stage chip) Possible
Short on a 5 V sensor reference loading the internal supply Less likely

How to diagnose P0606

Have the battery and charging system tested. Voltage codes such as P0562 or P0563 often show up together with P0606.
Clean and tighten the battery terminals, and check the engine and module ground straps for corrosion.
Use a scanner to see which module stored P0606. It isn't always the engine computer; the transmission, brake or body module can set it too.
Look up service bulletins and software updates for that module. Reprogramming fixes many P0606 cases but needs a dealer or a shop with programming tools.
If sensor codes show up as well, a shop can check whether a shorted sensor is pulling down the module's 5-volt sensor supply.
Replace the module only after all of the above. A new one must be programmed to your car, usually by a dealer or a shop with programming tools.

Vehicles that report P0606 most

Vehicle	Years	Reports	Median miles
Ford Fiesta	2011–2016	6	80k
Ford Focus	2012–2014	4	46k
Chevrolet Silverado 1500	2019	4	7k

Counts of owner complaints to the NHTSA that mention P0606 (36 in total), not failure rates: popular models get more complaints simply because more of them are on the road. Models with fewer than 3 complaints are left out.

Reading the code

P: Powertrain
0: Generic (SAE) code
6: Computer and output circuits
06: Specific fault

Questions drivers ask

Can I drive with code P0606?

Drive only as far as a shop, and gently. The car may go into reduced-power mode and, in rare cases, stall or not restart, which is dangerous in traffic. If it stalls, barely accelerates or doesn't respond normally to the pedal, have it towed.

Will my car pass an emissions inspection with P0606?

Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.

Often reported together

Codes that owners mention in the same NHTSA complaints as P0606. They can point to a shared cause, so it's worth checking them together.

C0021ABS Pump Motor Circuit Range/Performance4 complaints
P25A2Brake System Control Module A Requested MIL Illumination3 complaints

P0606 Control Module Processor

What P0606 means