Hello All, I have 92 SC400 with CEL and Trac Lights blinking on and off. I checked the codes and they are 21 and 28. I had both main sensors replaced at a shop with DENSO's from oxygensensors.com Disconnected battery, pulled fuses etc etc. The same codes back again before i made it back to the house. tried disconnecting battery again this time I left it off over night. NExt morning made it about 5 miles down the road and the CEL back on again with codes 21 and 28. unplugged connectors and cleand the male ends, repeated the fuse pulling and batttery disconnect. Guess what, codes 21 and 28 are back again.

My question, Is there anything else in the system to check, or is it possible that i was sold 2 bad sensors. I havent checked the voltage output yet, so if anyone know what they should be and which lead i should test, that would be greatly appreciated.

 

You really should have replaced all 4 sensors and not just 2. You may still have 2 bad sensors there.

 

I guess i need to find a money tree somewhere for that to happen.



There were no codes saying the rears were bad. and from what i found on other post, all say to replace the mains to correct the problem

 

It's a 92. That means 15 years of gunk and dirt and garbage getting all over them. Preventative maintenance my friend. SC's are not cheap to maintain. And if I recall correctly from when I changed mine. There was no code indicating upstream or downstream O2 sensor.

 

I hear ya. I guess I have to pass on getting the needles fixed for a while. You are gith they are not cheap to maintain. I just might have to stick it up for sale.

SO if i understand you correctly code 21 and 28 could mean any or all of the 4 need replacing

allthough http://www.troublecodes.net/Lexus/

Shows

code 21 Main O2S & Heater Signal

code 28 Main O2S

NOt getting codes
27 Sub O2S Signal
29 Sub O2S

far too many quirky things for only 155k

 

My bad on the codes

Yeah, not cheap, but maintenance and doing a lot of work yourself helps keep costs down.