500SL ABS / ASR / rough idle after battery died

[IanSpencer]

Hi all,

Over the weekend I went to start my 500SL (R129 / 1997) and discovered the battery had gone bad.
I connected a spare battery using some jump leads and managed to start the car. However, this seems to have caused the following issues
- ABS light on
- ASR light on
- rough idling / lumpy running
I have now replaced the battery with a new one but still the same symptoms

Some googling indicates that on some cars this is the OVP relay fuse(s), but I can't seem to find an OVP on this car? I have checked the 3 fuses (10A / 20A / 15A) on the module that is under the plastic cover by the bulkhead on the passenger side and they seem OK. I wasn't able to get the cover off completely though as it seems that you have to remove a lot of the trim around the bottom of the windscreen? So not sure if there are other modules / fuses in there to be checked?

Any advice gratefully received! I just hope I've not somehow damaged the ECU by connecting the spare battery?

 

[RichardF]

Try reading the codes 1st, the OVP relays were discontinued, about the time 5 speed gear boxes were introduced.

 

[ivan1983]

If you just connected a spare battery it is unlikely to have damaged any control units.

Have you tried driving the car?
If not things like the steering angle sensor will need to be re-calibrated.
You can do this by moving the steering wheel from lock to lock followed by a short drive to get a few wheel revolutions.

If this doesn't clear it you will need to get the codes read as suggested.

Lumpy idle could be down to stale fuel, once it's running get some fresh super unleaded in there.
I assume it doesn't have distributors so that's one less thing to worry about

 

[BTB 500]

Good advice so far - hope you get it sorted. I had problems with mine due to low voltage, although it was the roof/windows/roll bar that were affected (it had generated some phantom fault codes that had to be cleared via STAR in the end). Basically if you have mains power where you park it then a maintenance charger is highly recommended - I've kept mine on one since 2007. The battery was fitted in 2004 and is still going strong so the charger has paid for itself many times over, never mind preventing any more issues over the years.

PS your car is an SL500 - 500SL was the model name up to 1993/94.

 

[IanSpencer]

Try reading the codes 1st, the OVP relays were discontinued, about the time 5 speed gear boxes were introduced.

Thanks - will do. Can I use a normal ODB2 reader such as this one:
https://www.amazon.co.uk/dp/B01AC7I7BO/?tag=amazon0e9db-21
or do I need a special MB / Star reader?

 

[IanSpencer]

If you just connected a spare battery it is unlikely to have damaged any control units.

Have you tried driving the car?
If not things like the steering angle sensor will need to be re-calibrated.
You can do this by moving the steering wheel from lock to lock followed by a short drive to get a few wheel revolutions.

If this doesn't clear it you will need to get the codes read as suggested.

Lumpy idle could be down to stale fuel, once it's running get some fresh super unleaded in there.
I assume it doesn't have distributors so that's one less thing to worry about

Thanks - I will try and take it out over the next couple of days (weather was terrible today) and see if that clears the lights.

 

[IanSpencer]

Good advice so far - hope you get it sorted. I had problems with mine due to low voltage, although it was the roof/windows/roll bar that were affected (it had generated some phantom fault codes that had to be cleared via STAR in the end). Basically if you have mains power where you park it then a maintenance charger is highly recommended - I've kept mine on one since 2007. The battery was fitted in 2004 and is still going strong so the charger has paid for itself many times over, never mind preventing any more issues over the years.

PS your car is an SL500 - 500SL was the model name up to 1993/94.

Thanks - strangely enough I think it was keeping it on a trickle charger (CTEK) that may have killed the battery that was in the car - there seemed to be a slight hissing coming from it as if it was boiling / gassing internally? Which charger have you been using?

 

[alabbasi]

ASR/BAS and odd shifting usually caused by 3 things and if you have a code reader, it will give you the codes. You'll need one that can read codes through the 38pin connector

Faulty brake switch
Faulter conductor plate or plug leaking which is pushing atf into the TCM
Low voltage readings from a weak battery

As you're getting this in winter, i would suggest testing the battery first , then changing the brake switch before going into the transmission. Although a quick way to check the plug is to pull the TCM and see if there's oil in the plug connector.

FYI, Not to be pedantic, it's an SL500 if it's a 97 and there are a number of changes between the earlier and later cars.

 

[BTB 500]

Thanks - strangely enough I think it was keeping it on a trickle charger (CTEK) that may have killed the battery that was in the car - there seemed to be a slight hissing coming from it as if it was boiling / gassing internally? Which charger have you been using?

I use an AccuMate:

AccuMate 6V & 12V Battery Maintenance System

My SL is hooked up to it 24/7 (apart from when it's being driven of course!)



But any decent automatic maintenance charger should be fine. Ctek are normally pretty well regarded ... sounds like yours might have had a problem!

 

[IanSpencer]

Hi all,

Over the weekend I went to start my 500SL (R129 / 1997) and discovered the battery had gone bad.
I connected a spare battery using some jump leads and managed to start the car. However, this seems to have caused the following issues
- ABS light on
- ASR light on
- rough idling / lumpy running
I have now replaced the battery with a new one but still the same symptoms

Some googling indicates that on some cars this is the OVP relay fuse(s), but I can't seem to find an OVP on this car? I have checked the 3 fuses (10A / 20A / 15A) on the module that is under the plastic cover by the bulkhead on the passenger side and they seem OK. I wasn't able to get the cover off completely though as it seems that you have to remove a lot of the trim around the bottom of the windscreen? So not sure if there are other modules / fuses in there to be checked?

Any advice gratefully received! I just hope I've not somehow damaged the ECU by connecting the spare battery?

 

[IanSpencer]

Hi just wanted to thank everyone for the tips / suggestions / advice

I built myself a little "bleep reader" which showed no errors (despite the ABS / ASR lights being on), so decided to take the plunge and drove to the petrol station and within 100 yards the lights cleared and haven't returned

Half a tank of decent fuel plus a good blast down some quiet roads seems to have fixed the rough running as well!

 

[IanSpencer]

I use an AccuMate:

AccuMate 6V & 12V Battery Maintenance System

My SL is hooked up to it 24/7 (apart from when it's being driven of course!)

View attachment 90224

But any decent automatic maintenance charger should be fine. Ctek are normally pretty well regarded ... sounds like yours might have had a problem!

Does the AccuMate come with connectors that can be left permanently attached to the battery terminals as well as the croc-clip style connectors?

 

[BTB 500]

Does the AccuMate come with connectors that can be left permanently attached to the battery terminals as well as the croc-clip style connectors?

Yes it does. The long output lead from the charger ends with a plug, and it comes with two short flyleads that can connect to that. One (which I've never used) has croc. clips on the end, and the other (to be left attached) has ring terminals that the bolts on the battery terminal clamps go through. This flylead reaches into the boot on my R129, from behind the trim panel that covers the battery. When I got my charger there was an optional wall mount which is very handy, but not sure if this is still available: