Need some help with my new E420

[bill420e]

I have just gotten a 1994 e420 with ASR. Had a blast driving it for the last couple of weeks. But, a few times rough running and AC fan stopped working sometimes. Then ASR light, now Check engine and limp mode. Pulled code 17 and then code puller stopped working. Voltage was 14.7V running. All fuses good. Wiring harnesses replaced and rebuild throttle 6 years ago. I am thinking computer problem. Ideas?

 

[a777fan]

Re: Need some help with 1994 e420

I have just gotten a 1994 e420 with ASR. Had a blast driving it for the last couple of weeks. But, a few times rough running and AC fan stopped working sometimes. Then ASR light, now Check engine and limp mode. Pulled code 17 and then code puller stopped working. Voltage was 14.7V running. All fuses good. Wiring harnesses replaced and rebuild throttle 6 years ago. I am thinking computer problem. Ideas?

Bill,



Probably best to start your own thread on your issues.

 

[gsxr]

Moved to new thread.

DM code 17 does indicate a generic data exchange malfunction between computers, but you'll need to get a hand-held blink code reader to pull codes from all 6 powertrain modules, clear all codes, and see which codes return. See the stickies at the top of the "De-Coding" forum for details on how to do all this. It will be difficult to diagnose without getting all the codes cleared up.

New harness is good, but a 6-year old ETA rebuild isn't a guarantee that everything is still OK there, but the codes will help figure this out. If the NSS isn't recent, that's another common culprit for limp mode.

AC fan, do you mean the blower motors for cabin air, or the twin electric fans in front of the condenser? This is probably not related to the running issues.

 

[bill420e]

Thank you. As I mentioned, the code blinker is not working now. I will try other pins and see if maybe the blinker will work for them this weekend, but for the basic codes, you hold down the button for 3 seconds and then nothing. Usually, I would get one flash or blinks for a code number. No response blink or blinks now. The car does start and run, but in limp mode.

I am not real used to these forums, but I love working on old Mercedes and have a few from 1959. This 95 is my newest car.

 

[gsxr]

Make sure you are plugged into the correct sockets, if using the 1mm pins (no breakout box). It's easy to get the numbers mixed up. It would be very unusual to have the blinker box not work on any modules, unless the blinker box itself is defective (also not likely).

 

[gerryvz]

My home-made blinker box was working sort of intermittently for a long time. I took it apart and found that a couple of the wires inside had become disconnected, and this was because I had not taken the time to properly solder and/or shrink-wrap them -- just choosing to twist things together and use electrical tape. Properly connecting things solved the issue.

This may be the issue with your blinker-box. I agree with GSXR that it's unusual not to have the box work on any modules, unless the box itself is not working/connected correctly.

Cheers,
Gerry

 

[bill420e]

Thank you. I was able to access the 38 pin with blinker and had lots of codes, but was able to erase all but two. Pin 6 6 blinks and 33 blinks. I get for 6, left front axle solenoid valve and 33, CAN data line, short or open. Car was driving great with one or two moments of bad idle and HVAC issues which may be very separate. The outside temperature light does not work on the dash and it is my understanding that the HVAC diagnostic uses this. HVAC blower does not come on usually, but sometimes all works well. ASR and ABS lights are on and car is in limp mode. This is a 1994 or 1995 e420 with ASR. Any ideas?

 

[gsxr]

Thank you. I was able to access the 38 pin with blinker and had lots of codes, but was able to erase all but two. Pin 6 6 blinks and 33 blinks.

Sometimes you need to start the engine afterward to make codes clear completely, but this is usually only on the DM (pin 19).

I get for 6, left front axle solenoid valve and 33, CAN data line, short or open.

Those are both unusual... first seems to indicate an issue with the ASR hydraulic unit, second makes me suspect the ASR module (or E-GAS module).

Car was driving great with one or two moments of bad idle and HVAC issues which may be very separate.

Engine running, HVAC issues, and limp mode are three separate issues that are likely all separate.

The outside temperature light does not work on the dash and it is my understanding that the HVAC diagnostic uses this. HVAC blower does not come on usually, but sometimes all works well.

The outside temp indicator on the dash, and also the engine temp gauge, both use dedicated sensors that are not connected in any way to either the engine controls or the HVAC systems, which each uses their own dedicated sensors (yes, that is 4 separate sensors total).

ASR and ABS lights are on and car is in limp mode. This is a 1994 or 1995 e420 with ASR. Any ideas?

ASR+ABS lights and limp mode sure sounds like you should be getting a lot more codes than just #6 and #33 on pin 6. DM code 17 also points to a module issue. For grins I'd disconnect the battery negative cable, check both sides of the battery positive terminal to make sure the nuts are tight, and remove / clean / re-seat all four modules in the CAN box. Makes sure the modules are ALL the way seated when re-installing, you should feel them bottom out, if any are too tight to push in by hand use a rubber mallet (GENTLY) to tap them all the way down.

You're at the point where if you lack a digital scanner (SDS C3 or similar), I'd be tempted to swap out the ASR module and E-GAS modules with spares. Both are relatively inexpensive on eBay or from forum classifieds, but when you don't know if your existing ones are good or bad, and you don't know if the "new" replacement is definitely good, that can add more mystery. Oh, for grins, also check all the fuses too. Rule out the easy stuff first.

 

[bill420e]

I am back in town and ready to work on the car more. I had already taken out the computers and made sure connections were clean and put back. I do have a scanner that I use with newer cars (OBD2) and it looks like I could get an adapter cable. What might be the cost for a SDS C3 scanner? I also have Indy dealers who have better scan tools and work on these cars all the time. Is there more information to be obtained in this case with a better or different scan tool? I have two of the computers ordered and on their way; I am told they work. I have not found an E-GAS spare yet. I had also very carefully checked the battery connections and cleaned them. Battery is good with 12.7 volts after sitting.

How would one check the ASR hydraulic unit? I was not even aware that there was a valve that could effect the front wheels. I thought that the braking was just activated on the back wheels in heavy acceleration. this is indicating one of the front wheels.

I have not thought much about the HVAC, but I know I can pull the instrument cluster and check for connections. The lights in the cluster do not work and it is dark (maybe the reostat). I do not know the location of the HVAC computer. As I said, sometimes that HVAC works and sometimes it does not, but the temp light on the dash is off and has no display. I can get to that later.

 

[gsxr]

I do have a scanner that I use with newer cars (OBD2) and it looks like I could get an adapter cable.

Won't work... don't waste your money. The 124.034/.036 are OBD1 and will not communicate in any way with OBD2 tools.

What might be the cost for a SDS C3 scanner?

Full setup (laptop, multiplexer, cables, software) generally runs around $500 or so. Maybe less if you're handy with computers and don't mind piecing a kit together. There are some extensive threads on this topic. The SDS C3 is what the dealer has, it will do everything possible on the car.

I also have Indy dealers who have better scan tools and work on these cars all the time. Is there more information to be obtained in this case with a better or different scan tool?

Depending on what exact scan tools they have, you might get some useful information, but if you're paying them per hour... buying your own C3 starts to look more enticing.

I have not found an E-GAS spare yet.

There are usually a few for sale on eBay (link), you can find them under ~$100 or so if you are patient. Gerry just sold a couple in the classifieds on this forum.

How would one check the ASR hydraulic unit? I was not even aware that there was a valve that could effect the front wheels. I thought that the braking was just activated on the back wheels in heavy acceleration. this is indicating one of the front wheels.

I don't know how to check the ASR hydraulic unit, other than to swap the ASR module and see if you keep getting the same fault codes. The unit is ASR+ABS combined so it affects braking at all 4 wheels; although as you sait ASR will only affect the rear wheels.

I do not know the location of the HVAC computer. As I said, sometimes that HVAC works and sometimes it does not, but the temp light on the dash is off and has no display. I can get to that later.

HVAC is controlled by the pushbutton unit, above the radio. However, if it's the blower/fan that works intermittently - either zero air, or works fine... it is likely either a cracked 30A strip fuse, or a blower motor with brushes worn out. It isn't likely to be anything else, so I'd check those 2 items first.

 

[gerryvz]

I have not found an E-GAS spare yet.

https://www.500eboard.com/forums/showthread.php?t=12889

 

[bill420e]

I have not driven the car around because of the limp mode. I wonder if I should to make sure all codes come up. I will try trading computers when I receive them.

RE: HVAC, I did replace the 30 amp fuse with a new one. I did remove the blower and test it with 12v and it blows. the brushes were worn, but had good material left. The blower turned stiffly, but that may have not been bearings and could have been magnets. I replaced the transistor/control but still sometimes works and sometimes does not.

 

[gsxr]

RE: HVAC, I did replace the 30 amp fuse with a new one. I did remove the blower and test it with 12v and it blows. the brushes were worn, but had good material left. The blower turned stiffly, but that may have not been bearings and could have been magnets. I replaced the transistor/control but still sometimes works and sometimes does not.

Hmmmm. That is odd. It does sound like the blower motor may be nearing the end of its life though. The blower does not spin very freely when new, but also should not be particularly stiff. If you don't have a good one in hand to compare to, it's difficult to tell what is normal. I'd hate to recommend you throw ~$250 at a new Behr blower, but it's still my top suspect if the blower randomly stops & goes. The bushings at each end can be lubed with ATF but that won't help the stop+go problem. Sometimes the brushes may still have life left when the blower is otherwise shot; you check those mostly to see if either brush is at the end of travel in which case the motor should definitely be replaced.

The regulator (transistor/control) failure mode is either dead blower all the time (not intermittent), OR it runs at a fixed speed at all times (will not change to max or min speed). A bad regulator wouldn't cause the blower to stop & go.

Another remote possibility is a failing ignition switch. I really doubt this is your issue, but next time the blower stops, trying turning the ignition key back towards "off" just a TINY BIT. Like, a couple fingers worth of light pressure... not enough to make the engine shut off, or all the dash lights come on. If the blower magically comes back to life, try turning the key back towards "start" and see if the blower stops. If you can repeat this scenario, the ignition switch is dying. I've only seen this happen once, on a car with over 200kmi, and I can't recall if anyone else has ever reported the problem on the forum.

FCP is having a July 4th sale with 15% off, I think $215 is the lowest price I've seen for a 1994-95 Behr blower motor. They have a lifetime warranty as a bonus:
https://www.fcpeuro.com/products/mercedes-hvac-blower-motor-behr-1248200608

 

[bill420e]

I thought of another odd thing to share with all of you. When checking the pins for codes, pin 14 was hot with 12 volts. I did not expect that. Is that the case with other 420s or have we found a short?

 

[gsxr]

I thought of another odd thing to share with all of you. When checking the pins for codes, pin 14 was hot with 12 volts. I did not expect that. Is that the case with other 420s or have we found a short?

Pin #14 is empty. You may want to double-check the numbering...

 

[bill420e]

Car is running great now with switch of asr computer bought for $35 on ebay. HVAC was fixed with new blower as advised.

Plug 14 is hot with 12 v. I was just checking codes for fun today and plug 16 is a little how (very dim). I guess there is some short that has not stopped the car yet.