'94 E420 - Check engine light - checked analog codes and :

OK, I checked code 19, it says "Injector open or short circuit or emission control adaptation at limit"and code 20 is "Vehicle speed signal missing".

I reset the codes and then after two trips code 19 came back on. Anyone have any idea what this means, or what needs to be checked next?

Note: The car appears to run fine (though the accelerator has always been a bit touchy - I've owned the car for about three thousand miles, so I'm not sure how it should be).

Thanks -- Greg

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Greg Stein
'94 E420
'86 420 SEL
'79 300 TD

If your speedometer is working no need to worry about #20 unless/until it comes back. #19 could be bad wiring harness if original. Next step would be to check codes on other pins to see what else you get.

Check my main web page (about half way down) for details on the #19 problem and a solution.

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Regards . . . . JimF
-------------------
'94 S500 Cpe

Visit my Mercedes Web Page

Code 19 is an adaptation limit excess code..it is also common on that chassis b/c the ECU had a small percentage +/- lee-way for limits before popping the code. That can be expanded to a larger % by changing the chip in the ECU [ do a search on code 19/JimF here]...

..but , before going that route, you want to check for BOTH vac leaks AND fuel pressure. A vac leak will cause ECU adaptation beyond limits to correct for the lean condition caused by the leak, and a bad FP regulator will cause a rich condition by leaking gas into the vac port of the reg or allowing too high of a FP. That rich condition will also try to correct , but if the system has to correct too much , same deal...pops the limit reached/exceded code.
So, I would check for both vac leaks everywhere and then I would check the FP regulator and pressure.
If the engine has many miles , then it is just in need of a higher adaptatation value than the ECU is capable of and the chip w/higher % limit can be done..but don't do that until you have checked the above first, as you may not even need higher adapations % limits.


EDIT *

Jim F and I were typing in the same time frame, so his Posting is the search notation I was referring to............he has those chips, if neeed.

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A Dalton

I've got a spare wiring harness, so I'll go ahead and replace that as well as check for vacuum leaks and fuel pressure.

Is there a way to double check whether or not that chip is the problem?

Thanks! -- Greg

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Greg Stein
'94 E420
'86 420 SEL
'79 300 TD

I certainly would make sure your vacuum lines are good. Don't forget the 'nipples'; they get small cracks and are hard to spot. Might just replace all of them.

The DTC#19 is not associated w/ a wiring harness . . . but if it NEVER been replaced, now is a good time. If it HAS been replaced, there's no need to do it again.

Not until you remove it from the fuel computer. I can assure you that's it's not the improved version.

__________________
Regards . . . . JimF
-------------------
'94 S500 Cpe

Visit my Mercedes Web Page

If you find vac leaks or FP faults, just clear the code and run it ..if it was cured , the code will not come back up b/c you have solved the problem and the system has re-adapted within the limits.

However, as JF has stated , they found that as the engine wears , the adaptations limits of the original were found to be too close a limit for normal adaptations and by upping the +/_ percentage of his modofication, it gives the systsem more limitation % lee-way.
I have even seen a dirty a/filter bring on a code 19 with the OEM system..
But is your engine management system is in real "On The Money" running conndition, [ meaning no leak, wear, fuel mix, etc], then it will run within OEM limits just fine. There are many out there that do not bring on a code 19 and they have the OEM set-up.
A trick to do after you find any leaks or FP problems , is to get that code 19 cleared and then after you get a single Flash [ designating No Codes Stored], you then wait 2 secs, press button 6 sec , turn off key for 2 secs , on for 10 secs and start car...this will clear the adaptation memory back to mean [ zero] so the ECU does not have to readapt with drive cycles..you will then know you are starting with a zero base-line and if it hits adaptation limits after that memory clearing, then it has come from zero, not from the OLD adaptation memory that was set before the remedy...
Less chance of getting a false code while the system re-adapts that way..

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A Dalton

OK,
Replaced the wiring harness, the old one wasn't all that bad off, but when I bought the car I was warned that the time was ripe (14 years) to replace it.
Checked the fuel pump pressure, just fine (~50 psi). Checked the intake manifold vacuum. seemed good (~15 Hg in, no wobbling), didn't spot any leaks, though the engine runs pretty much the same even when I've disconnected a hose.
I ran through the other diagnostics (thanks to the tested I built thanks to Dean's schematic). On pin 6 I got code 13, stop lamp. On pin 7 I got codes 5, 6 and 11. The only one that seems relevant is code 11 which says "Fuel safety shut-off to LH-SFI control module". Pin 19 yields code 19, back to "Injector open or short circuit or emission control adaptation at limit". Code 20 has not (as yet) returned. Pin 30 yielded codes 3 and 8, which I don't think are relevant to the problem at hand.
G. Johnson has suggested the air mass sensor, though I would hate to replace such an expensive item without further testing. Does anyone have any suggestions on what I could look at next?

JimF, what would cause the emission control system adaptation to go beyond the limit? I would rather get it back in limit (if that's reasonable) than to change that chip to accept a wider range (which is what I understand it would do).

Oh, I assume I'm doing no damage driving the car.

Many, many thanks. -- Greg

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Greg Stein
'94 E420
'86 420 SEL
'79 300 TD

Did you check the FP reg port/line when checking the pressure.??

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A Dalton

I used the test port that's on top of the engine pictured below. Is that the one you mean?

Greg

Attached Thumbnails

 

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Greg Stein
'94 E420
'86 420 SEL
'79 300 TD

Yes, you could replace the MAF and that probably will add a few points (ie, raise it abit) to the S/A number and, while you're replacing, do the O2 sensor. Both 'fixes' are not cheap but the MAF is the expensive item.

The MB dealer fix for your problem is replace your fuel computer module, so if that's their solution, my is EXACTLY the same, except it's much cheaper but it does the same thing b/c it's the eprom that's in the new F/C module.

Leaving the way it is will do not damage but if you have to SMOG your car, it won't pass w/ DTC#19 present.

__________________
Regards . . . . JimF
-------------------
'94 S500 Cpe

Visit my Mercedes Web Page

And all these codes came after you replaced the harness and cleared all the codes? Still runs OK? CE light on or not?

No..that is fuel rail pressure Test Port Fitting.

What we always check first when there is a fuel trim adaptation limit code
on EFI systems is the Fuel pressure REGULATOR vac port.

They are notorious for leaking by and that leak causes unmetered fuel to get sucked into the engine intake thru the vac hose , causing a rich condition that can be beyond ECU correction b/c it is raw gas that has by-passed all control systems [ un-metered fuel]
So, the test is to simply take the vac line off the REG. and look for eveidence of gas in that vac line..if ANY, replace the reg..it is leaking by...I also run the engine with the vac line OFF to see if any gas comes out the port..if YES , same deal..replace regulator..
That should have been done when you did the fuel pressure test b/c FP test is done with BOTH vac line ON and OFF. [ along with 30 min rest]
If no leak at reg , continue on with other possibles ..I mention this simple test only b/c of it fequency of failure rate on these and I have seen so many MAF and other sensors changed in vain b/c this FIRST test was not addressed.
Takes all of 15 secs., so I recommend getting it off the table ...
If it is bad , I also recommend my previous memorey Reset of ECU for Zero/Mean...after reg replacement.

http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=2EI1B4MYE2ER0X76YW&year=1994&make=MB&model=E-420-001&category=C&part=Fuel+Pressure+Regulator

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A Dalton

Arthur,

Yes, I disconnected the vacuum line from the regulator during the test. I didn't notice any fuel, but then I wasn't looking for any.

Deanyel,

I just reset the one code 19, not the others. I'll also try Arthur's suggestion of resetting the adaptation memory back to mean.

BTW, is there a simple method (eg disconnecting the battery for a minute) for resetting all of the codes?

Thanks -- Greg

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Greg Stein
'94 E420
'86 420 SEL
'79 300 TD

Fault codes on the 38 pin connector are erased just as they are with the built-in pushbutton - by holding the button down for 8-10 seconds after reading the code.