Sometimes a problem is detected that only lasts for a short time, even as low as a fraction of a second but the computer recognizes it, sets a code and turns the check engine light on. It can be something that the computer turns a relay on and the computer is looking for power output at the same instant and it takes a slight amount of time for the relay to close. The program should be written to only turn the check engine light on when the problem lasts for a significant amount of time. This might be what the mechanic is referring to.

I have a 2006 that gives me a code every now and then. It might go a month of a couple of weeks. Mine is a P0042 and is part of the oxygen sensor heating circuit. It is never an active code when checked. It seems to be peculiar to 2006. The computer checks the circuit on startup and occasionally sets the code. I have a scanner connected and the code is never active meaning there is no problem at the moment. The code will take several starting cycles to clear. It is supposed to be a timing issue in the computer and there was a software update for it but the dealer can't seem to find it. The same timing issue causes a problem with the remote start if the defroster or AC are on in hot or cold weather.

It doesn't really cause any problem but it is annoying.

 

There is no POO42 code as such - but there is a P0042 (the last 4 chars are NUMERIC).

The P0042 code isn't listed in our HHR code list - the P0042 code refers to a 3rd O2 Sensor - and the HHR only has two as far as I know.

 

That could be P0036,P0037,P0038,P0054,P0141,P0140. They all have something to do with the #2 O2 sensor heater.

I'm guessing you mean P0140, which really doesn't. What it means is that the #2 O2 sensor is wearing out, or your Throttle Positions sensor/butterfly is fluttery, or your battery is low.


If you mean P0420 that randomly pops up, then direct your GM shop to TSB 04-06-04-073 that they should have actually read instead of reading just the title. Can't read not can't find.

It says in part:




End of hijacked thread.

 

Perhaps dB can confirm the code prior to any further guesses.

 

And it looks like he is actually meaning P0420!!!

 

Whoever moved the post here, made the questioning title.

 

Somebody else started this thread. I was explaining in the other thread that it could be a random code that means nothing. It could also be a problem with the computer not being programmed with enough time for the sensor involved to reach the correct reading.

On my 2006 it is a P0042 code that pops up from time to time. That is for a third oxygen sensor which the vehicle doesn't have so it is obviously a software problem.

Another code that it randomly sets is a P0138 which is an out of range oxygen sensor. It is supposed to set after a voltage below 1.2v for more than 10 seconds but it comes on within 5 seconds of starting the engine. Real time data shows no problem and I can clear the code and not have the problem for a month or two.

There was a bulletin on an ALLDATA site about a problem with the timing functions in 2006 models where there wasn't enough time for everything to reach the required values. It shows up first when the remote start is used. The vehicle starts and shuts down. It also starts on the second try and shuts down. It doesn't set any codes but someone found that it was because the oil pressure isn't high enough soon enough. It happens in cold weather when the vehicle sits outside in -15F for several hours.

I arranged to leave it at the dealership one night when it was supposed to be cold and they were scheduled to work on it first thing in the morning. At the dealerships, you don't get to talk to the mechanic that will be working on it. You talk to a service writer who might not know the first thing about a vehicle. Due to poor communication from the service writer, someone checked which vehicles were scheduled to be worked on first the following morning and brought it into the shop despite the keys being marked to leave it outside overnight. Off course the remote start worked fine in the shop so they never checked for updates. It was the last night of cold weather that year so there was no use to try again.

 

Thank you for your confirmation of the code and the explanation.

 

Which is the TSB that I posted.

There is updated software the TSB explains how and where to get it.

You stated that the shop couldn't find it. If that is true they don't know how to use the Tech2.

 

I don't know what got communicated to the guy who was working on the vehicle. The dealer seems to have the service writers diagnosing the vehicles and telling the techs what to do. It was a service writer that told me the service bulletin that ALLDATA referenced wasn't available or didn't exist. Too me, whenever they have a vehicle in the shop, they should be installing the latest version of the software updates. It was in for the keylock cylinder last time. There are some stickers in the engine compartment saying what campaigns have been completed in earlier visits.

I might have to try again but it's a pain. Dealers don't want to pay mechanics which might be the reason they don't want customers to have contact with mechanics. They also don't want customers to know how long they actually worked on the vehicle. They don't even want customers to wait for their vehicles. Automakers don't want to allow outside shops to receive and install updates. GM is saying it will provide over the air updates by 2020 so vehicles don't have to be taken to a dealer but that will likely only be for new vehicles.