97 E320 immobilizer issues
 

I have a 97 E320 doner car that I'm using the engine and trans from. I'm in the process of removing all the stuff I do not need from the interior side of the harness. Somehow something shorted and blew the 50A fuse on the K40 relay and after replacing it I have a crank no start issue with fuel pressure and spark. This is indicative of an immobilizer issue.

How can I reset the DAS/immobilizer? I have the key and access to the entire harness.

Looks like this posted twice. Unsure how to delete sorry.

Would a manual help ? i have found information inside it on the alarm google this -
Model 124 Maintenance Manual Index

There isn't any reset needed.

Was the engine able to run immediately prior to the fuse clearing?

Also 97 is all to it's self in terms of DAS. A diagram for a 97 C280 / SL320 / S320 would be very similar in terms of the engine / DAS.

To delete a post, press EDIT at the bottom of the post, DELETE , Then scroll down to confirm. ( Or very similar )

It's a car I'm trying to clean up the harness in to remove the engine and harness for a swap. It was running before that bus popped. I had not made any new changes to it. However I'm suspecting I need to reinstall the lock module from the passenger footwell. However I need to be sure I'm resetting it properly as I make these changes. This could be a real nightmare if I'm not careful about that.

Details matter here. So the car was running, fuse cleared, replaced, car won't run? As in there were no other changes? What made the fuse clear? I'm pretty sure the E320 fuse you replaced is for the electric air pump if so, it would appear someone inserted a 50A where a 40S should be.


If this car is a 97 with a metal key and internal RFID chip, no resetting is required nor is the lock module involved. I've swapped the engine computer, DAS box and key a few times on me SL to test used parts.

Is there an antenna ring around the ignition lock cylinder? This antenna ring leads to the DAS box to the left and behind the instrument cluster. The DAS box is about 4 " x 5 " x 1 " and is black plastic.


You really need to study a wiring diagram for this car.

Anyone know where to find a wiring diagram for this? If I could find a complete one this would be much easier.

As for what happened exactly it started and ran one night, then a few days went by and I decided to pull the column, no changes to the wiring other than disturbing it so something may have been grounded when it shouldn't. I went to start it and it didn't even want to crank so I jiggled the starter hot and both wires from the battery. I had a crank no start issue. I checked all the fuses and the 50A one on the K40 relay under the hood was blown. With that replaced no change.

I have the basic key with the key ring and the module in the dash.

If there is no immobilizer issue then something else is causing the injectors to not work.

Update on this.

I put 5 gallons in just to be sure and it's the same issue. It did fire on starting fluid.

Make sure you are getting power to the injectors, this is a +12V rail to all injectors and comes from a fuse somewhere. The computer grounds the injector to fire it.

Ok thanks for the info. I'll check that out tonight.

Tested to have 6v at the injectors in run and when cranking.

So this is telling me the immobilizer is not sending the right signal to the ECU. So frustrating how there is very little information on this.

You should be seeing 12 V on the power side of the injector wire. You are likely picking up stray voltage. Digital meters are very sensitive and will show voltage that goes away if a load it applied.

I've given you lots of information concerning DAS. You _NEED A WIRING DIAGRAM_, a scan tool would be helpful as well.

Also, why did you work on the column with the car powered up?

Making this work isn't difficult. The greater picture is that if you can't solve this problem, whatever your conversion plans are will fail.

Thanks for letting me know I should buy a tool that costs half of what I have in the entire project. If it's really this simple I shouldn't need a tool to know how to reset the alarm and trace issues with the immobilizer.

I'd love a wiring diagram if I could find one. Unfortunately I can't.

Why was I working in the column with power on the car? I wasn't. I josseled all kinds of crusty home made starter wiring, from the PO, while removing it then powered it up. I don't even know if that 50A fuse on the K40 relay blew then but the lead to the starter was definitely not in good condition and may have shorted.

If it has 6v when it's powered on I agree that is odd. It maintained 6v while cranking. So yes that could be a short if it does in fact need 12v rather than 6.

You can't afford to get snarky with the only knowledgeable person helping you.

A good scan tool will show if the ECU is released by the DAS box to run the car. The DAS or alarm system don't need reset, it is plug and play if the key matches the DAS and DAS matches the ECU. I've shuffled these 3 parts between cars and never had a problem. I've even gone so far as to put a 97 C280 and 97 C36 AMG ECU in my 97 SL320 and had zero starting issues. The fuel maps were all wrong but the car ran and drove.

Also, if the key / DAS / ECU are miss matched the engine will run for 3 seconds then shut down, you car isn't doing that.

There are usually CD manuals on E bay.

On my 97 C280 / SL320, the 50A ( is 40 A on my cars ) fuse on the K40 is for the electric air pump relay / motor on my cars and won't affect starting of the engine.

If there was a " short " you would have melted wires / fuses that have cleared. Calling this issue a short shows a fundamental lack of understanding of electrical systems. Couple this with the lack of a wiring diagram and this project is doomed to fail.

I appreciate the help but I do not appreciate the tone.

A short can very easily cause a low voltage issue especially if there is high resistance in the short. Remember that V=IR and the equations for series and parallel circuits. A short with a bad connection will cause a voltage drop and not melt wires. Think of how when you run too much load on a circuit the lights dim. There is either a voltage draw(could be a short) or the multi meeter is wrong when reading injector voltage but not when reading battery voltage.

Got it. It gets really frustrating on my end going through the same explanations over and over then you not having a wiring diagram. Dig around on e bay for a service manual CD. The electrical section is called ETM . A wiring diagram is critical.

You are speaking of a compound problem that , while possible, isn't common. In any event, get a wiring diagram. If e bay does not pan out, MB has a online manual service and All Data / Mitchel have consumer grade one car access for something like $ 30 per year.

Well I do appreciate any help I can get on the issue. This is something I'm working on in my free time and hopefully I'll have a bit more of that next week.

Correct. That's my understanding, so I don't think it is the immobilizer. Since it runs with starting fluid the issue seems to be fuel. I don't know how to interpret the 6V you measured on the injectors. If you are measuring the high side then I think it should be higher. If you are measuring the low (switched) side then I don't know how a multimeter wold interpret the PWM signal there. I think you would see a pulse. I would verify the fuel pump runs with the key on and measure the fuel pressure.

The security/ECU/immobilizer/fob/IR/chip issues in these cars are a nightmare however. Mostly they prevent the owner from using their own car. That is my experience anyway. Hopefully that is not your problem.

The 98 + cars with a " smart key " fob are the difficult ones, 97 is simple.