Still not sorted light 21 engine electonics been to 4 different garages none have readers that go back before 2000 my scanner can't find any codes how do I find what I'm looking for replaced starter because it was playing up replaced lambert senser still light on also abs light come on intermittently any suggestions please

 

I can only relate a few stories from my '98 S70.
Got an oxygen sensor code, replace same. Still got code. Disconnected/ reconnected battery, still got code. Called my mechanic, he said to tighten gas cap, if that doesn't work to replace the cap. It was loose, code went away.
ABS modules are notorious. Check the gazillion posts out there. Some time after repairing mine I had a similar problem, turned out to be a bum wire to a rear wheel sensor.

 

not all code readers can read ABS codes. For the 850s, common issues are 1) wheel sensors which can go bad or get fooled by dirt/grease on the inner side of the hub 2) ABS controller boards can develop cracks in the solder leading to intermittant fault codes 3) you could have an ABS system issue - pump/valve body. Most likely its either a sensor or the controller board. When you say lambert sensor - do you mean "lambda sensor" which is another term for the front oxygen sensor? Lambda refers to the feedback signal from the sensor to help the ECU manage fuel trim. If you have an intake air leak/exhaust leak/EGR tube issue etc, that can throw off the accuracy of the signal which will throw a code - usually a long term lean fuel trim code. Still don't know what you mean by light 21 unless you are referring to the traction control enable/disable light. Make sure you don't have the traction control switched off. If the light remains, this is likely related to the ABS light since the tracs control uses the ABS system to slow the spinning wheel and throw power to the opposite side. My bet is that you fix the ABS controller/wheel sensors and your tracs light will go away as well.