C124 ABS light on

[Ade B]

It appears the CE has sensed that we have spent money on something else (bought a new bathroom today) and immediately spat its dummy. The ABS light is on..

From things on here, first port of call is OVP relay fuse and then the relay itself. This was replaced 2 years ago before I picked up the car.

Can anyone tell me what is disabled apart from ABS (impressive test skid undertaken earlier) and the cold start mechanism - which will no doubt cause trouble tomorrow

Also is there anything else I should check?

TIA

Ade

 

[Ade B]

update (for anyone that's interested)..

Cold start is disabled, if it didn't have 6 cylinders I don't think it would tick over at all - never seen a car tick over at an indicated 0 rpm . Once its cleared its throat though, sits at a happy idle of 6-700 rpm..

Battery is fine giving 12.75v

ABS is also out so I'm pretty sure its OVP related..

Checked OVP relay which from what I can gather is the large relay under a cover on the far right of the component rack - ruski sit was down earlier. Both 10A fuses seem fine, relay is MB branded (made in Hungary) and is shiny and new looking with a red base - of course I didn't take the part number before putting it back together

Have I checked the correct relay, is there any way of checking the relay itself (there's no way into it without bending the tangs on the metal casing - and where's the best place to get a new one?

Advice would be most appreciated, and Happy 2009!


Ade

 

[Ian B Walker]

Don know if this will help but have experienced a similar problem. The pins on the OVP relay go into two sockets. The three pin socket is the one that gives grief with abs. Make sure that the pins are clean and that the relay is fully home and not just touching, pushing the socket downwards.

 

[Ade B]

I may have been checking the wrong relay... the one I have has 9 pins and is only one socket - I'll go and take a pic and maybe someone could point me in the right direction..


Cheers,

Ade

 

[Ian B Walker]

the nine pin socket is split into a six and a three. Its the three that causes the grief.

 

[Ade B]

pic attached:

The bit I was tinkering with is the red topped relay at the end - am I barking up the wrong relay?

Ade

 

[Ian B Walker]

Right relay. as per pm, yep ok.

 

[grober]

check the output voltage side from the OVP to see if there's a conspicuous voltage drop across it. The ABS units can be sensitive to supply voltage and this will trigger the fault light. Then try disconnecting either the abs unit or idle actuator to see which of any is pulling down the voltage. IIRC The idle actuator works by the ECU controlling the earthing side-the supply remaining constant.

 

[Ade B]

check the output voltage side from the OVP to see if there's a conspicuous voltage drop across it. The ABS units can be sensitive to supply voltage and this will trigger the fault light. Then try disconnecting either the abs unit or idle actuator to see which of any is pulling down the voltage. IIRC The idle actuator works by the ECU controlling the earthing side-the supply remaining constant.

OK.. how do I do that then, I've got a multimeter would you be able to tell me which bits to stick the probes onto..

Also, which bit is the ABS unit and which bit is the idle actuator - the Haynes manual is predictably not much use on electrics and the Ruski site was down earlier..

Both ABS and cold start are not functioning.


Ade

 

[grober]

here is a picture of the idle speed actuator http://www.detali.ru/cat/oem_mb2.as...GM=717.450&CT=M&cat=520&SID=09&SGR=060&SGN=03
It will have an electrical plug/connector with 2+ connections. If you disconnect it one should read battery/ OVP output voltage the other is connected to the ECU so exercise care. If you remove the OVP [momentarily for test purposes] this voltage will disappear and let you know you are looking at its output voltage. While the idle actuator is disconnected (OVP IN PLACE) does the ABS warning light go out? If not then the problem probably lies with either the OVP itself or the ABS controller or the actuator unit. This is all assuming a certain circuitry but impossible to know without seeing the actual setup?

 

[Ade B]

thanks I'll give that a try in the morning


Ade

 

[Ade B]

here is a picture of the idle speed actuator http://www.detali.ru/cat/oem_mb2.as...GM=717.450&CT=M&cat=520&SID=09&SGR=060&SGN=03
It will have an electrical plug/connector with 2+ connections. If you disconnect it one should read battery/ OVP output voltage the other is connected to the ECU so exercise care. If you remove the OVP [momentarily for test purposes] this voltage will disappear and let you know you are looking at its output voltage. While the idle actuator is disconnected (OVP IN PLACE) does the ABS warning light go out? If not then the problem probably lies with either the OVP itself or the ABS controller or the actuator unit. This is all assuming a certain circuitry but impossible to know without seeing the actual setup?

Silly question, but will I need to take the air filter housing off to get to the idle speed actuator?

Cheers
Ade

 

[grober]

If you have the old pancake style [ oval shaped ] filter on the top of the engine the answer is yes-you will see things a lot better that way.

 

[Ade B]

Update - bought a new OVP relay from MB and swapped them over. ABS light has gone out.

Will be nice to have working cold start in these sub zero temperatures, not to mention ABS.

Thanks for the input guys.

Ade

ps - sodding push in plastic cover behind the battery is a fine piece of design (not) maybe mine has gone brittle over the years, but it is now practically in 2 pieces. Its the only thing that I don't like about the car...

 

[bolide]

Glad you got ot fixed

the Ruski site was down earlier..

I think that's due to low gas pressure...

Nick Froome
www.w124.co.uk

 

[230K]

ps - sodding push in plastic cover behind the battery is a fine piece of design (not) maybe mine has gone brittle over the years, but it is now practically in 2 pieces. Its the only thing that I don't like about the car...

When you take that plastic cover off you should write top /front on it, it seems to go in what you think is upside down then it just falls in place and it is a good fit.

Glad you got it sorted and thanks for completing the circle for people in the future.

230K