'95 E420 - DM Codes 3, 4 & 25 - What to do next? - PeachParts Mercedes-Benz Forum

Syntax26 · #1 04-30-2008, 08:43 AM

Anyone like to advise on my next step? What to replace/repair?

'95 E420 - 100,000 miles. Replaced engine wiring harness, ICM & spark plugs (Bosch F8 DC4) 5,000 miles ago - car was running great. CEL light came on - been pulling DM codes 3, 4 & 25 - erase them - they come back within few miles. Checked plugs and vacuum lines - all appear good. Cleaned MAP - same codes. Always runs 92 octane or higher.

Symptoms: Car runs great at mid-high RPM after accelerating. Car runs great idling in park. Problem is rough idle when in gear, brake on (such as at stop sign) AND upon accelerating from standing start or very low mph (10 mph or less).

Car still has original O2 sensors - but I'm hesitant to replace since not pulling codes for them.

Should I start with replacing knock sensors? (Code 25).

If lambda control is indicated (Code 3) - what do I actually replace/repair?

Any advice would be appreciated. THANKS!

By the way - I put a sport suspension in the car (springs, sway bar, shocks, brakes) and love it. Like a new car - so highly recommend anyone thinking about it.

deanyel · #2 04-30-2008, 10:30 AM

It sounds like you have pulled only the DM codes. You should build the code reader if you haven't already and pull all the codes. Lambda is the O2 sensor.

JimF · #3 04-30-2008, 10:53 AM

As deanyel recommended you need to pull codes from the EA, LH modules for sure. You can build the home-brew readed described in MENU#2. It's worth the effort.

Bosch specs O2 sensors for 60Kmiles so you could be due. Also don't forget the MAF sensor. . it might be contaminated, Menu#4a.

The rubber 'tips' of vacuum lines usually develop cracks which are not visible until you actually bend them a bit.

If Lambda is not functioning, I'd fix that first and that will probably fix the knock sensors.

Syntax26 · #4 04-30-2008, 12:38 PM

DeanYel and Jim F....

Thanks for the very quick replies of advice.

I'll do the O2 sensors first (I should have known the lambda code is for the 02 sensors!)

And about the radio shack reader - would you believe I bought the parts and started to build it about 10 months ago? LOL! Life got, and always gets, busy...and I ended up putting the project aside.

By the way Jim - I've read your website a few times - that is where I learned about the MAF contamination and what educated me to buy the CRC cleaner last night.

So again, THANKS VERY MUCH for your time and advice. I appreciate it!

Jim V.

JimF · #5 04-30-2008, 03:12 PM

You're entirely welcome. . .

OK, now is the time to finish that 'project' . . . it's a handy tool.

Let us know what happens.

Larry Delor · #6 04-30-2008, 10:11 PM

Unless something changed between 94 and 95. you should just have 1 O2 sensor, and it is in a PITA location. Lifting the car up, and dropping part of the exhaust will be on the menu. (if I find the guy responsible for the location of said sensor, I will give him a swift kick in the rear)

emerydc8 · #7 04-30-2008, 10:42 PM

The O2 sensor on my 1993 is really easy to change. I guess MB engineers discovered this and decided to redesign later models to make it much more difficult.

deanyel · #8 04-30-2008, 11:06 PM

I'm sure the 93s and 95s are the same. It's not a terribly difficult job if you have the right tool - a 22mm open offset socket, something like this - http://buy1.snapon.com/catalog/item.asp?P65=&tool=all&item_ID=74621&group_ID=1448&store=snapon-store&dir=catalog
I could see having to drop the exhaust if you didn't have one.

Syntax26 · #9 05-05-2008, 04:12 PM

Guys...

Well I can confirm the '95 E420 O2 sensor location was designed by satan himself. Topside of the exhaust - vicinity of the "y" connection - pre-converter (naturally). The threaded bung is actually in a small recess - making it IMPOSSIBLE to get a wrench on. So you're forced to use a socket. Because of the wire - crow's foot socket! THE TOOL POPULATION GROWS AGAIN! ha ha!

Can also confirm - just one sensor (pre-cat) on this model.

Unfortunately...can't yet address whether the new sensor fixed the code issue - since soon as I got this done - I had to put brakes & shocks on the Landcruiser. (Snapped 2 caliper bolts - had to drill and tap threads in the steering knuckle - talk about PITA!)

Just wanted to say thanks for the help and advice - I'll chime in with "worthwhile" commentary on the diagnosis and fix when I get the car off the blocks tonight.

Jim

Syntax26 · #10 05-09-2008, 02:17 PM

Dean, Jim & Larry,

Thanks for your input before...I do appreciate it.

As I mentioned when I started this post, I was pulling DM Codes 3, 4 & 25 on 8 pin connector (CEL on). I replaced fuel filter, spark plugs, distributors & caps, and 02 sensor. Cleared codes on 8 pin connector - drove car - codes came back in normal cycle.

Per your advice..next step was to finish building Jim F's home tester. I did so and pulled codes from X11/4 38 pin connector. Below is list (I include ALL operating pins - even if not seemingly relevant) (all code descriptions come from Baum manual):

Pin 4: Code 11 (Secondary air injection system, open or short circuit) - Cleared

Pin 6: Code 13 (Stop lamp switch) - Cleared

Pin 7: Code 5 (Stop lamp switch) - Cleared
Code 6 (Starter Lock-out/backup switch) - Cleared
Code 14 (Closed throttle position contact switch) – Cleared

Pin 8: Code 10 (Voltage Supply for LH-SFI control module interrupted or voltage supply for fuel injectors interrupted) - Cleared
Code 11 (Voltage supply for accessory equipment interrupted) – Cleared
Code 12 (Voltage supply for ABS, ABS/ASR or ASD control module interrupted) –Cleared

Pin 13: No Codes

Pin 14: Initially light lit continuously, but when checked AFTER finishing all other clearing – No Codes

Pin 16: No Codes

Pin 17: Code 5 (Knock sensors 1 and/or 2 faulty) – Cleared
Code 7 (Knock output switch in ignition control module faulty) – Cleared

Pin 19: Code 3 (Lambda control faulty) - Cleared
Code 4 (Air injection system faulty) - Cleared
Code 25 (Knock sensors faulty) – Cleared

Pin 30: Code 8 – wouldn’t initially clear – but when checked AFTER finishing all other clearing - No Codes

AFTER CLEARING ALL CODES - I DROVE CAR AND CEL CAME ON IN SAME CYCLE AS BEFORE (few miles driving - 3 ignition starts). Codes pulled from DM are same as before, to wit: 3, 4 & 25.

So.........any advice or guidance on where I should go next? I'm thinking knock sensor replacement and re-examination of ground wire connections .

By the way, I put in new engine wiring harness, plug wires and ICU about 5,000 miles ago and car ran well with no CEL over that time.

Also by the way - my experience level is such I can tear down and rebuild a Chevy small block (to the crank) and it works fine.

Also also by the way - these electronic issues with MB become somewhat addictive, don't they? I knew I was anal before...but I find myself reading everything I can find on how these controls operate. Yet - their just not straight forward like a good old chevy mouse.

Well, thanks for your time if you read all the way through.

Jim

JimF · #11 05-09-2008, 05:19 PM

Well reported!

Does the AIR work when you start the car cold? In any regard, check the vacuum connections to the AIR pump; make sure that all is ok. Also check the changeover valves that drive the pump.

The "lambda" system not working; check the MAF for contamination, see MENU#4a. Try to clean it and what happens. The Hot Film ('95) versions don't seen to clean as well as the Hot Wire ('94), so it might have to be replaced.

Don't overlook the "brake switch" and "neutral safety switch"; easy to replace and can (do) cause Lambda problems.

Syntax26 · #12 05-09-2008, 07:13 PM

Jim,

Why thank you for the compliment on "well-reported". As I mentioned, I'm somewhat of an anal guy. LOL!

I'm home from work and about to head into the garage...trusty golden retriever as my assistant. (He is more intelligent than I...even with automotive matters).

AS to the secondary air injection system: I don't know if it works upon cold start. I'll try to figure this out. And the valves.

AS to the MAF contamination: I'm pretty sure the/this '95 E420 is hot wire versus hot film. So according to my Bentley E-Class Bible, and my understanding of looking down the MAF throat and seeing the wire configuration (V shaped). When I mentioned before I had cleaned it...I had read your website (4a) and ended up buying the CRC cleaner. But...I was only able so far to spray it down the throat (through the screen)...NOT able yet to disassemble and get right to the wire. Maybe this weekend (even though I'm working a car show.)

As to the brake switch: So ironic you mention this can (does) have an effect on lambda readings, in light of the fact I've been serially working on this issue WITHOUT thinking there could be any connection/relation. My warning light comes on for outside lights - comes on upon brake pedal activation - and despite switching all known brake light bulbs (including the often over-looked "rear window" bulb)...the problem has persisted. A few days ago I decided to undertake replacement of the switch ONCE I solved the ignition/injection code issues. So mabye I should "un-serialize" my process and jump on this right away? Sounds like it. So I ask (since I haven't yet had time to do the reseach): Where might I find this switch? I was going to start my search in the master cylinder area.

Well, let me end by returning a compliment to you. I joined this site about a year ago - and during that time I've read hundreds (if not thousands) of your posts/replies assisting others. I have a great deal of respect for you and your efforts (and the efforts of some other gentlemen I see offering much assistance on here (ADalton, Deanyel, Larry Delor, and some others). And I've read your website many times where you share your knowledge. I think this is the way all people should live their lives - helping others - whether it be in a forum like this, or elsewhere. So if I was a betting man, I'd bet your friends respect you?

So thanks...I'm going to get to work. By the way, I tried to help someone out on here today - referred him to the "code reading instructions" I had picked up on here that were posted by someone else. Hope it helped him.

Jim

JimF · #13 05-09-2008, 08:17 PM

The brake switch has fixed a lot of problems such as yours. And, as you read in Menu#24, the NSSw fixed my problem also. So both are candidates for change.

The brake switch is in the driver's well; the NSSw is on the tranny's left side at the linkage.

Tnx for the words; you mentioned the 'big-three' and there are others including the tech's of this site. Excellent help given whenever it's needed.

Larry Delor · #14 05-09-2008, 10:26 PM

You can get a little closer to the wire in the MAF, by prying off the snap ring at the top of the MAF (utility knife worked for me) - the mesh then just lifts off.

I read that the wiring harness was replaced....but....what about the ETA (electronic throttle actuator aka throttle body to some)?

Just for grins, I would be tempted to check the fuses on the main module (in the module box - the box where you would think the battery ought to be) - that, and I would make sure the modules are nice and secure in their slots.

emerydc8 · #15 05-10-2008, 01:57 AM

I read Jim's article and bought a can of that CRC MAF cleaner, which is still sitting in my garage--unused. I was under the impression that you had to take the MAF off the car to clean the hot wires. I guess it can be done on the car without any damage. Is the snap ring something that can be reused? Is the snap ring on the inside of the MAF at the edge of the screen?