What is error code 51 & how can I fit it? - 1989 Oldsmobile Cutlass Supreme

I'm not too keen on airbag repairs but I hope this link will help you get the answers you need to get you on the way to your repairs :o)
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Airbag Code 51 flashing and a fix ( & moved here) - TCCoA Forums

Ignition bypass error.42,incorrect MEM-CAL 52.

TYPE: OBD 1 Code 13 etc & read for hours

Could Type: 1989 Cadillac OBD 1 Codes

It's all there on the internet

Codes,Problems & Solutions--- dozens-- if not
hundreds of sites,forums,tech info,etc

You use Google

Type: 1989 Olds Cutlass OBD1 Code 51

As you said I believe you have a problem with the Exhaust manifold between gasket and engine block. I do not know your model but if you have a turbo engine probably the turbo either is leaking or broken.Having these problems,surely the vehicle become very thirsty on fuel and low power. Please do not use your hands to check any exhaust leak,you surely burn seriously your self. Ask your mechanic to do the correct job.

12 just means the system was reset recently 55 mean end of codes so don't worry about them 2 however code 51 is an oxygen sensor error (O2 Sensor) a bad or shorted O2 sensor can cause it to run very bad and get poor gas mileage.

I have a 1990 4Runner A/T and solved the error #51 replacing the Throttle Sensor. Don't forget to connect a Ohmeter and adjust this sensor to its right ohmeter values for a properly installation, this sensor is not a PLUG & PLAY stuff. Oh, and the idle was fixed too.

the code 51 is your automatic shutdown relay control. and the crank position sensor is on the bellhousing behind the passenger side valve cover.
Have you replaced any relays? Let me know.

chek battery voltage with engine running if over 14.5 volts the altenator is bad and will need to be replaced high will cause all of these codes

You need to ring the Peugeot Dealers, as I had that problem with my Nissan radio on my Nissan. The dealers were able to immediately provide me with the right code to input and radio has worked no problem since. When I disconnect battery I always need to re-input the same code.
If your Blaupunkt wasn't Manufacturer fitted, then whoever of your previous owners who fitted the stereo would have the code, or have you tried Blaupunkt themselves, don't know if they keep codes?