Does anyone know why the Cylinder Head Temp always seems to read 244F?

 

That's the upper limit of the 8-bit A/D converter (actually 255). And it doesn't take very long to reach that, at which point the Motronic ECU ignores the CHT for fuel compensation. Unless you're seeing a fault code for the CHT?

 

Thanks for the quick answer to my question. I do not have a fault code but I am trying to diagnose an intermittent poor idle. I have noticed that when the car is idling poorly that the 02 sensor readout is stable or counting down from 100 or so. Not sure if this indicates a bad 02 sensor or if something else is causing the 02 sensor to produce a constant signal. When the car is running correctly the 02 sensor fluctuates between zero and 130 (approximately) which I think is normal. Thanks.

 

A properly functioning O2 sensor will bounce back & forth constantly. The DME diagnostics should notice if the signal stays constant for a number of read cycles and would then throw a intermittent fault code. In addition to a faulty (the most likely case) O2 sensor it could also be a sticking injector or an air leak in the intake. There is also a chance of interference from the ignition wires but that tends to zap everything (and is the reason for the little black wire holding clips on the valve covers). Definitely check the connector in the back of the engine compartment before you replace anything. The contact pins tend to tarnish (you can clean them with a pencil eraser) which leads to problems with the electrical signal moving from the sensor harness to the engine wiring harness.

 

Jason- I always follow the Scantool threads just out of interest.
My questions is how do you know this stuff? Your knowledge and the general depth of knowledge on the forum is astounding.

 

Jason, Thanks for the comments. Are you recommending that I clean the 02 Sensor connector contacts? That is a difficult task on the engine harness side of the connector. The contacts are also protected from being easily cleaned by the connector housing. Oh well, no one said it was going to easy, just making sure you think I should try cleaning the 02 sensor connector contacts.

I was also curious about the 8 bit A/D used in the scan tool. If a 16 bit A/D (?) had been used would that have allowed for higher temps to be displayed? Does the Hammer also have this limitation? Just wondering....

Waiting to hear how you answer Twood BTW. Thanks for knowing a lot of stuff!

 

I have had the Scan Tool interface for a number of years now but it has not had a lot of use.

I have spent the last few days getting my Scan Tool up and running on an IBM Laptop and USB RS232 converter.

Everything seems to be working now and I have been looking over old threads and something is confusing me. I see all the readouts that people have posted but I have found very little information on what it all means. I see different readouts for the O2 sensor or the MAP sensor and others.

It great having the Scan Tool but without some knowledge of what these reading mean or what they should be, they do not help me much. Is there somewhere I have missed where these reading are explained or tell me what the norm is?

Okay I understand if a fault comes up saying that my left mixing sensor on the CCU is not working or I have a hall sensor fault ( I am also subscribe to the Hall Sensor Fault thread) but the reading from the Input Channels are sometimes similar to others and sometimes very different and I have no idea what it all means.

Is there any light in this dark tunnel of understanding the reading that Scan Tool gives me?

 

bump on both this question and the one directed at JA who I agree is encyclopedic

ie I just found a #25 ie temp sensor fault - what now?

 

cleared the fault (temp sensor)but it resurfaces and adaptation doesn't complete as it say soemthing lie engine wasn't upto temp altho it was after a 20 min drive.

Also my WOT & Idle switches don't seem to be changing ie closed all the time- I haven't put my AFM back yet - could that be related?

 

The intake air temperature sensor is part of the AFM. Once you put that back the fault code should clear.

 

aha! Thanks again Jason

 

I guess when they removed the AFM, the wired up this ad hoc AIR TEMP SENSOR.
Now it maybe its not attached to the motronic - hence the lack of signal to the scantool.
Some of my wiring and a vacuum pipe go to a fuel mgmt system (Diktator - last pic, under passenger seat).

Simple/silly question - Can I test this air temp sensor with a multi-meter? Apologies but I am an electronics neophyte!
I'll find out from the Diktator guys if they use the input - ie it may be going to their box.

 

Hi all,
finally got around to working with the Scantool. So, i have only run it with the ignition on and all was good (no error codes) except CCV which had three - so I cleared them - tested again and error code 15 keeps coming up - which is the rear fan sensor.
Now... dumb question time - given that I have removed the rear heater fan and replaced it with a carbon fiber heater bypass tube, and simply cable tied the old wires out of the way - I am assuming this is why i am getting this error and can safely ignore it?

 

A missing rear fan will trip a fail-safe function in the Climate Control Module and stop the front interior blowers if you set the temperature **** to higher than minimum. Maybe you don't need heated air in your area.
However, the rear fan also have a cooling function, I guess this is important in hot climates. Have a look here for details on the rear fan operation.
Cheers,
Tore

 

Thanks Tore. I thought long and hard before the rear heater fan delete. In fact, after I swapped it out, I kept it aside just in case I need to put it back !
I went through winter here in Australia and it was MORE than enough heat without the rear fan blower.
We have just had nearly two weeks of 30 - 40 degrees (celsius ) and the air conditioner and fan work perfectly too - so, i won't be putting the rear blower back again.
I did the wiring modification to the CC module (as per rennlist forum post) and it works really well.
I thank you for answering my question - I will ignore the error message from now on.
Now to go for a drive and do the adaptation