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Billy, Trainer/ Master Technician
Category: Mercedes
Satisfied Customers: 3498
Experience:  Trainer 8+ years, master tech. 10+ years, SAE member
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My 1991 SL500 sometimes has a problem selecting reverse or

Customer Question

My 1991 SL500 sometimes has a problem selecting reverse or park on the auto box. It is most likely to happen on the first short journey of the day, with the result that I have to leave it in the neutral position. I then cannot remove the key and have to wait with the ignition off for a while and hope the lever will slide forward if I need reverse. Any ideas please?
Submitted: 4 years ago.
Category: Mercedes
Expert:  Shantal-Mod replied 4 years ago.

Hello Barry,

I've been working hard to find a Professional to assist you with your question, but sometimes finding the right Professional can take a little longer than expected.

I wonder whether you're ok with continuing to wait for an answer. If you are, please let me know and I will continue my search. If not, feel free to let me know and I will cancel this question for you.

Thank you,

Expert:  Billy replied 4 years ago.
Hello Barry and welcome! I'm Billy and i will assist you with this.

My apologies for the delay, thank you for your patience.

This is the R/P lock solenoid causing the problem.

You need to get to the shifter assembly, and check whether this solenoid is getting power (12v) when not working, and then it would be stuck or seized, try some WD40 or equivalent, and if this does not work, replace the solenoid. If however, you are not getting power, then check the wiring connector on it, make sure you have clean and tight contacts, and then check whether the brake lights are working, if not, replace the brake light switch on the brake pedal .
If the brake lights are working, then you would need to check the wiring from ETC (transmission control module) to the solenoid (i would start by making sure i have clean and tight contacts at the connector of the ETC). The ETC is located in the front of passenger foot well under a tread plate.