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cc/isc module faulty ?

6K views 35 replies 6 participants last post by  mercron 
#1 ·
Hi everyone

I've got a problem with my 1994 Mercedes E320 (might be a 1993 since thats what it says on the throttle body)
the problem being that when in park or neutral the idle jumps between 600 rpm and 1100 rpm.

I have rebuilt the entire wire harness for the engine, rebuilt the wire harness for the throttle body, new gasket for throttle body, checked for vacuum leaks everywhere without any success, changed some vacuum hoses and fittings anyway and still the problem doesn't go away

error codes are on pin 8 :
4 : MAF (yes i have three of them and all of them a shot)
13: air-fuel mixture too rich or too lean

no error codes on pin 14

the thing is that when i put it in Drive or Reverse, everything is fine, idle is where it's supposed to be and everything
so I'm suspecting that the CC/ISC module is faulty, or can the MAF make such a difference in idle speed ?

one final note is that the Cruise Control doesn't work at all
 
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#3 ·
There is no traction control on it (which i think that ETA means) it doesn't even have the ASR throttle body, and the OVP relay is swapped out from my spare parts/donor E320 (same year different options on it) it was the first thing that was swapped out (also changed the fuse in it)
 
#4 ·
and sorry for double posting but i need to correct myself regarding your reply Jayare, the ETA is completely rewired with brand new wires, and the car runs fine otherwise, it's just the idle at park and neutral that is jumping around, and I was actually a bit afraid to test the cruise control after i rewired the ETA
 
#5 · (Edited)
Normally you will get error code number 2 from pin 14 if your non-ASR CC/ISC module is faulty. But, your CC doesn't work too. This could be a faulty CC stalk.

Idle fluctuations in P and N without CC/ISC code could be the MAF, MAF wiring, intake air leaks, or your ECM. It does come up as an error from pin 8.

Also, error 13 from pin 8 indicates faulty fuel injectors or fuel pressure regulator. Have you checked those?

http://manual.startekinfo.com/manual/JSP/e2/1_1/m11.jsp


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#6 ·
Normally you will get error code number 2 from pin 14 if your non-ASR CC/ISC module is faulty. But, your CC doesn't work too. This could be a faulty CC stalk.

Idle fluctuations in P and N without CC/ISC code could be the MAF, MAF wiring, intake air leaks, or your ECM. It does come up as an error from pin 8.

Also, error 13 from pin 8 indicates faulty fuel injectors or fuel pressure regulator. Have you checked those?

STAR TekInfo


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I do know that the MAF is bad, it give out WAY too high voltage, but it is still the same problem if i remove the cable from the MAF (which should make everything go to standard pre programmed values right ?)

MAF wires are new point to point

ECM has been replaced from donor car

intake has been checked all over (also replaced from donor car)

fuel injectors would make the car misfire (which it doesn't do)

fuel pressure regulator has actually not been checked
but i would suspect that it throws this 13 code due to the MAF giving WAY too high values, thus resulting in a way too rich or way to lean burn or am i wrong in suspecting that ?
 
#9 ·
You cant fix an idle control issue with a fuel mixture that it outa wack becuase that will cause the engine to idle outa wack. No getting around this issue, the MAF has to be fixed or what ever is causing your AFR issues. Then if you still have an issue with the idle go back to the idle control. But the idle control cant control an engine that is too rich or lean, that alone will cause surging.
 
#11 · (Edited)
Yes, you can reset a new ECM with ignition ON by clearing all codes, holding button down on the diagnostic port for 6-8 sec, turn off engine min 2 sec, turn on min 10 sec, then start. That's the ECM.

To reset a new CC/ISC module, turn ignition On for 90 sec then start.

ECM adapts to other components like MAF, O2 sensor, crank position sensor, engine temp sensor, transmission shifts, error codes from diagnostic module much longer.


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#13 ·
alright so here it is
i've installed the new MAF, and done a couple of runs with it, first run it went beautiful on idle, but there was just no power in it when i accelerated, it got up to 80 degrees C and still was perfect on idle

turned her off went and did a few things for a couple of minutes then wanted to go for another run, started her up (temp still being at 80 degrees or around there) and idle went back to going between 600 and 1100 arouund, but went out anyway and then there was power in the engine on that run

went back home power still rough, turned her off, took off air filter, started her up and went for another run, and she ran a bit weird but not out of the normal during driving conditions but when i came back idle was still jittering so i checked the MAF connectors and there was only around 8 volts going in, and 5.42 coming out to the ECM !!!!!!! holy shite

so i replaced the OVP again too and checked the connectors coming into the MAF and they were back to around 12 volts
as of writing this, has only had her idling up to around 40 degrees C and she idles nicely

going to do some more test runs later to see how she behaves, it smells on the exhousts like shes still running a bit rich though, so what do you guys think ? o2 sensor ?
 
#14 · (Edited)
Are you absolutely sure the "rebuilt" wiring is not the culprit here?

Particularly, the throttle body wiring gauge needs to be exact and twisted in the right order.

FWIW, I have never seen good long term results with "rebuilt" especially DIY rebuilt wiring on these cars.

The big clue is that your cruise is not working.
 
#15 ·
actually not tested cruise after the wiring got rebuilt on the ETA, and yes it is spot on correct,went out to check the O2 sensor which was between 0,40 volts to 0,73 volts which seems to be accurate and correct, temp was around 50-60 degrees C and was having weird idle again with 8 volts coming into the MAF *sighs*
 
#16 · (Edited)
It still doesn't sound like a CC/ISC module issue. Normally you'd get code 2 for that from pin 14. Did you clear all codes and checked again?

Did you check your fuel pressure regulator for leaks? Unplug the vacuum hose and observe for 3 to 5 minutes if there are any fuel coming out of it.

If your MAF is now getting the right voltage and you're still having idling issues not showing any codes, you may have faulty coils, wires, and spark plugs. They can go bad without throwing any codes. I'd check those too.


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#19 ·
ok so ran the engine for about 10 minutes
cold start idles perfect
voltage in to MAF is at 12.05 volts
pulled the FPR vaccum hose, nothing came out of the FPR while running it

however MAF voltage drops to 8 volts in when starting engine a second time hot...
that is very weird in my opinion
 
#22 ·
Yup, check your EGR. Make sure it's working and not clogged. You should feel it pulsate and suck vacuum from the pipe facing the firewall at operating temp.

Also, check that your engine coolant temp sensor is working too. Check resistance at different temperature.


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#25 ·
The EGR valve sits on the exhaust manifold, around cylinders 5 and 6. The EGR pipe is virtually impossible to see as it snakes behind the block and then underneath the intake manifold.

It's a real bugger to deal with that pipe, which is why most people rotoroot their old pipe vs. replacement.

However, that part was redesigned and I always urge for replacement especially if a headgasket job is on the radar.

I have not seen the redesigned pipe clog up.

Even if your car is a Euro spec car, you have a emissions package including air pump and EGR. Otherwise, code 5 would not be triggered. The only exception is bogus codes being generated by eco junk wiring, but I am going to assume your car is no longer being strangled by the eco junk crap stuff they put on at the factory.
 
#29 ·
correct all the bio junk is gone and away, however the code 5 on pin 8 was triggered after i had been measuring the lambda voltage, the air pump is actually disconnected from the wiring due to it shorting out the magnetic clutch when the bio junk was there, the spare parts engine i got (which is out of the car and sits on a wooden pallet) has a stuck magnetic clutch too so i didn't think it was worth replacing when i had both engines out, and i was looking at THAT engine to see the EGR valve and it's piping.

On code 5 for the EGR, the diagnostics can only measure the faults from the switchover valves pulling the vacuum from the EGR valve. Check all connectors and vacuum hoses. You should also be getting error code 39 from pin 8.


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shit forgot to mention that the code 5 WAS on pin 8, have not checked pin 14

The ECT sensor on your car should have a 4 pin connector right on the thermostat housing beside the 1 pin coolant sensor that goes to the dash gauge. The ECT affects startup, warmup, and normal temp fuel to air mixture.


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that is really good to know, that might be why the engine is running on a rather rich mixture still.
I thought the only things that affected the air/fuel mixture was the MAF, Lambda and that small air temp sensor in the intake pipe.

classic test for EGR is to start the engine, let it idle disconnect the other end of the vacuum line that leads to the actual EGR valve, and conenct it to a mity-vac. pump a vacuum, the engine shoudl stumble and stall. if it doesn't, very high probability that the EGR pipe is plugged up near where it goes into the intake manifold

more involved tests involve testing the EGR control valve mounted on the front of the head to verify it opens/closes as needed... on my volvos there was a test mode you could put the ECU into which woudl open/close the EGR so you could test it. I haven't found anything like this on the M103 or M104 yet.
I actually have alot of background repairing volvo's (since my dad has a preferance for volvo's and has been a mechanic since the 70's) also Opel and SAAB, however sometimes mercedes seems to live in their own little corner when it comes to mechanics, and that's what sorta intrueges me, first car I ever had was actually a 1981 Mercedes 280 SE, I loved that car.

this next bit is to all of you
anyway I do have a theory though, since the voltage to the MAF drops SIGNIFICANTLY when i hot start the engine, i figure that there is a voltage regulator feeding the MAF somewhere (followed the wiring on the spare parts car as far as i could) which would make sense since otherwise your MAF would blow out the first time your car battery/alternator gives up/overcharges, however i think my voltage regulator to the MAF has given up due to the wires actually catching on FIRE at one point, so i wanna know if anyone of you could check their voltage TO their MAF ? and post the voltages here on both cold start hot start and such, just to be clear i do not mean the voltage coming from the MAF to the ECM but the voltage going to the MAF on pin 1 and 2 on that connector, alternatively the small 2 pin connector that is LOW by the battery right next to the crank sensor connector ?
 
#28 ·
classic test for EGR is to start the engine, let it idle disconnect the other end of the vacuum line that leads to the actual EGR valve, and conenct it to a mity-vac. pump a vacuum, the engine shoudl stumble and stall. if it doesn't, very high probability that the EGR pipe is plugged up near where it goes into the intake manifold

more involved tests involve testing the EGR control valve mounted on the front of the head to verify it opens/closes as needed... on my volvos there was a test mode you could put the ECU into which woudl open/close the EGR so you could test it. I haven't found anything like this on the M103 or M104 yet.
 
#30 ·
the only voltage regulator is the one on the alternator, which manages the battery charging, and should limit the voltage to between 13.6-14.1 volts.

there IS the OVP which is a relay that senses high voltage and disconnects things. this is pretty fragile, and many folks on here consider them wear items that should be replaced every 5-6 years or whever there's random problems. on the CIS cars, the OVP only powers the lambda system, and the idle control, while on a M104 HFM, it powers the whole ECM and everything, so if it croaks, everything shuts down.
 
#31 ·
yeah, and just to be on the safe side i did replace the OVP relay to no result, without any affect
i just find it weird though that when the car runs perfectly, the maf gets supplied around 12 volts
while the rest of the car gets around 13 volts
however when the idle starts being jittery the MAF only gets 8 volts
while the rest of the car still has around 13 volts
that's what lead me to my theory
 
#32 ·
you're measuring that power at the red/blue wires on pin 2 vs the brown ground on pin 1 ? red/blue is directly connected to the output of the OVP, via the fuse on it. what did you replace the OVP with ? have you checked the fuse on the OVP ?

this same red/blue output of the OVP powers lots of other things, like the CC/ICS... so if the OVP failed open, that 8V you're seeing could be reverse leakage out of another device thats connected to the same circuit.
 
#33 ·
Yes, also red/blue vs permanent ground getting same result, the wires are rather hard to follow but that does make sense, the OVP relay was replaced with the one from the spare parts car I got, I know that car was running good but it had a bad gearbox, fuse was and has been checked and everything looked good on the OVP


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