# Need a CIS Expert!



## offroader944s (Jul 3, 2008)

I've done nearly all the tests and checks in the Bently manual on my 87 GLI with CIS E. All the inputs to the ECU check ok. Fuel pressure = 80PSI. The only thing I found, and it's a biggie, is the DPR current. Cold it starts at 150 mA and goes down to 130 mA and stays there. A check of the DPR current with 15k ohm resistor at the temp sensor with the fuel pumps "hot-wired", the current is 93mA when it's supposed to be 50-80mA. Need input from someone that's worked extensively with CIS.


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## Glegor (Mar 31, 2008)

did it just start doing this some day? or has it always been like this? did someone try and fiddle with the DPR its self?


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## offroader944s (Jul 3, 2008)

the day before it started running bad, it had a slight lean condition while warming up. the next day it started idling eratic then it would hardly run. was very rich at this point.


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## Glegor (Mar 31, 2008)

idk, sounds to me like its the DPR or something like that..


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## offroader944s (Jul 3, 2008)

I swapped a complete fuel dist. from a car that previously ran great. the tests on DPR checked out ok.


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## WaterWheels (Aug 14, 2005)

> The only thing I found, and it's a biggie, is the DPR current. Cold it starts at 150 mA and goes down to 130 mA and stays there.”” “”I swapped a complete fuel dist. from a car that previously ran great. the tests on DPR checked out ok


It would seem at this point that you are making a case for replacing the ECU. I would not do that just yet as you really need to look into all the “senders” which provide the ECU with information before deciding that it is itself bad. The “Cold start” readings that I found most times with VW is around 120mA, BMW seemed to be higher like 140mA. Remember that this is just what you should see when cranking a cold engine (like with the sensor disconnected). Once the key is released it should go down to around 80mA, that’s “Cold running”, and drop from there slowly until it gets to the closed loop reading (this could just quickly change when the signal from the O2 sensor is valid). So if your readings just hang at above 100mA I would suspect either some bad input or the ECU itself is faulty.

The differential pressure regulator (DPR) is not a sender but rather a receiver of information. I have seen cases where the screws which hold the DPR in place were swapped for normal metal screws, not stainless steel, and would do strange things due to the magnets causing the screws to also become magnetic. But nothing like this and you say you swapped in a good running unit already. I would run through testing all the inputs, water temperature, O2 sensor, etc. before anything else. Remember that testing the sender is fine and dandy, but also check the wiring. If the temperature sender tests OK but the wire has a break then as far as the ECU knows, the temperature is very cold. In any case it should drop slowly after starting and not stay so high.


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## dacolino (Jun 1, 2002)

following the tests you did, have you ohm'd out the differential pressure regulator? Simulate the same settings you explained in your first post for this test, but disconnect the test connector between the dpr and your multimeter, and check the ohms directly at the dpr. Should be 17.5-21.5 ohms, if thats out of spec it should be a faulty dpr. If that is in spec, check your ground for the cold start valve/thermotime, if good check the power supply fuse. If that is all good, id verify continuity between the ecu connector and the csv and thermotime, if you have continuity, then the ecu is faulty according to the book.


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## offroader944s (Jul 3, 2008)

did all the checks at the ECU input connector (25 pin). the DPR resistance was 18 ohms. all readings 
at the connector were in-spec. the grounds all had continuity and it had 12V at power terminal. 

If the ECU is faulty, what most likely caused this after 24 yrs of seemless operation? I've heard ECUs 
very reliable, so I suspect something else caused it to fail.?.?


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## WaterWheels (Aug 14, 2005)

offroader944s said:


> If the ECU is faulty, what most likely caused this after 24 yrs of seemless operation? I've heard ECUs very reliable, so I suspect something else caused it to fail.?.?


Nah. Out of 1000 in service over 24 years I would expect at least 100+ to just plain old fail. It is electrical and as such gets warm (that's why the heat sink on the end), maybe not to the touch but as far as electrical equipment is concerned. It lives mounted to a rolling metal box so vibration plays a factor. Then there are the parts which make it up, no they do not move like bearings, but they do go bad over time. Some may last 30, 40 or 50 years without any problems, but not all of them.


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## offroader944s (Jul 3, 2008)

Thanks for your help! I checked everything i could think of last night and all is OK. Have a post up for 
another ECU. Hopefully that will fix it. If not there will be a GLI for sale on VWV...


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## dacolino (Jun 1, 2002)

Sounds similar to my situation, let us know how it goes



> If that is all good, id verify continuity between the ecu connector and the csv and thermotime, if you have continuity, then the ecu is faulty according to the book.


It was brought to my attention that I mis-informed. Sorry, I should have proof read and would have seen my mistake.


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## ziddey (Apr 16, 2006)

Is your plug for the CTS perhaps corroded? That would cause an increase in resistance the ECU sees. I take it this problem is preventing you from going into closed loop operation? I had an 85 gli with the same setup, and with the CTS unplugged, I'd get about 150ma through the DPR. Didn't have the clip on the cts plug, so it fell off a lot.

Have you tried a resistance that would simulate warm running to see if you get 10ma through the DPR? One of my cis-e cars came with a paper clip shunting the cts plug, but since that's a lower resistance (none..), it may cause damage to the ECU. In my instance, it kept the car in warm mode though, and I got 10ma until the o2 came online.


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## offroader944s (Jul 3, 2008)

CTS=closed throttle switch??? If I remember correctly, I think the check at the ECU plug was continuity 
through this switch with throttle closed. All checks at the ECU plug were OK. I will check resistance in 
the wiring. I've had the water temp to approx. 120ºF and the temp sensor is giving the correct resistance.
Checked resistance at the sensor and at the ECU plug - same. Not sure how long it takes the O2 sensor 
to heat up and come online. I've read that OBDII cars are in closed loop in a matter of minutes. 

Will check your suggestions. Thanks for the input.


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## Glegor (Mar 31, 2008)

CTS = Coolant tepm sensor.


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