OBDII Readings

[MarkStock]

So I've gotten my laptop reading OBDII codes from my 2004 Ford Taurus (70k) & 2009 Mercedes CLK550 (35k) and have a few questions.

All of these readings are not while driving. Haven't had a chance to go out yet in either car, but will soon with a helper driving. The Ford has sat for a couple of days, the Mercedes was overnight.

1) Coolant temp Ford 60f, Mercedes 69f. Ambient seems to be 60f

Is this most likely just a sensor difference or possible after an overnight cool down? I'm going to check concentration and ph once I get a chance to go into the auto store.

2) Mass Air Flow on Mercedes was reading 0.2 lb/min on the Mercedes (zero on Taurus). With engine off does this suggest the MAF sensor needs to be cleaned?

3) Intake air temp on both was 85f in the garage while other temp readings (coolant, catalyst) were 60f. Does this make any sense? Is it something to do with the KOEO position?

4) My oxygen sensors read as follows:

Mercedes

bank 1 sensor 2 oxygen sensor short term .45
bank 2 sensor 2 oxygen sensor short term .45

Ford

bank 1 sensor 1 oxygen sensor voltage 0.010
bank 1 sensor 2 oxygen sensor voltage 0.010
bank 2 sensor 1 oxygen sensor voltage 0.010
bank 2 sensor 2 oxygen sensor voltage 0.005

I understand .4 is normal. Is something up with the Ford's sensors or is this related to the KOEO position? Also, one Ford sensor is reading lower than the others.

5) Intake manifold pressure registered at 28.6 on the Mercedes. Does this make sense when in KOEO?

6) What do you suggest I monitor when driving? Also, on the Ford, I can run a few tests (KOEO, KOER, ABS/TCS). Any clue on where I can find the operator instructions for these?

Thanks!

Mark

 

[yonyon]

Don't worry about those low O2S voltages. You hadn't started the engine yet so the sensors were cold and the pipes were full of air.

The KOEO and KOER tests on the Ford can give you a quick answer to the age old question "Did I fix it?" when the check engine light comes on. Treat these as a verification test. If the self-test throws a code before you do something to fix it and doesn't afterwords then you're probably good.

KOEO will pick up on simple electrical problems such as a short or leaving something disconnected. KOER can pick up on things that can only be detected with the engine running such as a wacky sensor reading, IMRC or EGR problem, that sort of thing.

 

[MarkStock]

Thanks yonyon!

I saw a video where during KOER the PCM is expecting the brakes to be pumped, the wheel to be jerked left and right, and the throttle to be floored.

Does that make sense or should I just let both KOEO and KOER run without intervention?

 

[yonyon]

KOER is expecting to see that, yes. If you don't it will complain (with a DTC) about it, but you'll know why. The same goes for OD off switch and 4x4 switch if you have them. It will also complain if you have the AC on.

 

[MarkStock]

But these things are worth doing so that the diagnostic checks the response, right?

So what is it expecting the operator to do during the KOEO test and the ABS test?

Or is it safe just to find out?

 

[yonyon]

It's perfectly safe to find out. It will probably just report no problem. KOEO wants engine stopped and AC off, ABS wants engine stopped.

 

[punisher]

Use the link function for long links to prevent formatting issues.

Anyways, as to the original post, pulling codes on a cold vehicle, KOEO or KOER renders any realtime codes irrelevent, stored codes are still a go. Either self test assumes an engine at operating temp, AC off.

Cold coolant temp/air temp means nothing. IAT usually reds high compared to ECT. MAF voltage KOEO means nothing as there are different null voltages for MAFs, just like DPFE sensors. Each calibration code expects something different.

Stepping on brake during test checks BOO switch (for converter unlock input), turning wheel activates the p-steer pressure switch(for idle speed compensation).