P0606 issue

[matuszyk]

Typically a P0606 means replace the ECU. I have a check engine light that gives a P0606 yet it comes on every morning and goes off half way through the day. It stays off the rest of the day only to come on the next morning again. It happens on hot summers and cold winters. The dealership swapped out the ECU but that didn't work (I got my money back!). I am getting tired of working on this. Suggestions?

 

[BlackWorksInc]

So usually a P0606 indicates that there's an internal issue within the ECM and that it needs to be replaced. The curious thing is that when looking in TIS under an '04 4Runner (like mine) the P0606 is simply listed as being caused by a ECM failing internally. But choosing a '07 4Runner (You didn't specify what year you had so I am just guessing the year) shows some additional information, so I think Toyota has not updated some of their older sections of the FSM on TIS to reflect new information regarding the P0606 (information that seems to corroborate your experience with this DTC.) So here's the following description and Troubleshooting table from TIS (I can't copy the whole section because of the way TIS is set-up.)

DTC P0606- ECM / PCM Processor

The ECM continuously monitors its internal processors (CPUs), A/F sensor transistors and heated oxygen sensor (HO2S) transistors. This self-check ensures that the ECM functioning properly. These are diagnosed by internal "mirroring" of the main and sub CPUs to detect the processors error. If outputs from the processors deviate from the standards, the ECM will illuminate the MIL and set a DTC immediately.​

DTC Setting Condition:

• ECM CPUs malfunction
• A/F sensor transistors malfunction
• HO2S transistors malfunction

Problem Area:

• Exhuast Gas Leak
• HO2S
• ECM

By any chance did you get any other DTCs or only the P606?

 

[matuszyk]

P0606

I always worry that I am not using precise language here. I get the P0606 off my meter and it indicates a ECU/PCM problem. When I look at the raw dfata I see a 0.000 volt reading for a Bank 1 Sensor 2 heated oxygen sensor (the rear one). However, when we swap out the sensor and test the new and old sensor we know it is good. We also checked the wiring up to the ECU plug and verify that it is good. Bottom line: I suspect a software issue that is causing the ECU to misinterpret the inputs.

But, I may be wrong....

 

[matuszyk]

P0606

PS

I have a 2005. Thanks for the thoughtful reply.

 

[stoyles13]

I have an 05' with P0606 as well. Have you figured this out by chance? The CEL would come on and off, but for the last 2 months I has stayed on :frusty: