021 pressure switch A7/3s1

[RobertK]

Hello,
I have a question about a recurring issue on my '92 Japan import 500E
The ASR and ABS lights getting on during driving, sometimes directy from start and sometimes after certain time.
After that the engine is in limb-mode.

With a diagnostic MB tool the following codes come up:


Two wheelsensors on the right together is a sort of miracle I think, but that last one: 021 pressure switch A7/3s1
Is it possible that my hydraulik ASR/ABS unit has a defect on the pressure switch which is installed within the unit ?

Does interchanging this unit with an other (good working) one make sense ?

 

[gsxr]

Two wheelsensors on the right together is a sort of miracle I think, but that last one: 021 pressure switch A7/3s1
Is it possible that my hydraulik ASR/ABS unit has a defect on the pressure switch which is installed within the unit ?

That's what it looks like. See if code 021 keeps recurring after you clear it, and fix the speed sensors.

Does interchanging this unit with an other (good working) one make sense ?

Only if the problem persists and you keep getting only code 021, then yes, swap the ASR unit. AFAIK you can't replace pressure switch A7/3s1 separately.

 

[RobertK]

Allright, I will do that. That speedsensors can not be related to that code 021 or are that independant faults in the ASR/ABS system ?
I forgot to mention that I assume that my ASR is not working. The light will never go on in the speedometer during full throttle. During starting the engine it lights up.

 

[gsxr]

Allright, I will do that. That speedsensors can not be related to that code 021 or are that independant faults in the ASR/ABS system ?

Likely separate faults, but you need to troubleshoot those and see what's wrong. They could be old codes unless you had cleared them recently. Since you have the HHT, view live data when driving to see each wheel speed, or jack the car up and spin each wheel while viewing data. Could be a bad connection somewhere.

I forgot to mention that I assume that my ASR is not working. The light will never go on in the speedometer during full throttle. During starting the engine it lights up.

The light won't go on unless you break traction, which won't happen at full throttle on dry pavement. Put the rear wheels in dirt, in 1st gear, and floor it... if it spins up with no ASR then yep, it isn't working. Note that if the ASR warning light is on in the cluster, you likely have no ASR.