Hi All,
I need help here. I've got a '94 855 Turbo w/ 215k miles.
I've had a chronic check engine light w/ codes 433 or 143.
Front or rear knock sensor codes. I've replaced them both
twice now, including Volvo's SB on the '94 KS. I've totally rewired
them and the code or codes keep coming back. I've come to the
conclusion that I have an ECU problem. Anybody have similar problems?
Will other ECU's fit, namely from a '95 or '95R? Will a later ECU
fix this?
Thanks alot
Rod Brehm

Somewhat common problem with lower quality gas. Have you tried premium? I know that your manual doesn't specifically say you have to, but may be worth a try. Your question in regards to the ECU from a later version 850 fitting your car has been asked before, but unfortunately the answer is NO. You might fit a '93 or even an early '95 but no others. The ECU and engine management as well as OBD are completely different. Actually, 4 systems are used 850's...Fenix 5.2 (for older 10 Valve Turbo's...we don't see much in this couuntry), Motronic 4.3 and Motronic 4.4 and the LH3.2- Jetronic system. The Motronic systems all use a single ECU to control the fuel and ignition functions. The LH3.2- Jetronic system (in your 850 (unless yours is a 10 valve- Fenix), the '93's and some early '95's) uses 2 ECU's- one for the fuel and another for the EZ-129 K ignition system. Your system uses 2 black diagnostic boxes under the hood to deal with these 2 systems and their fault codes. The Motronic systems use the mandated OBD-II system to read codes, etc. through a connection within the cabin. Hope this information helps.
--
1998 S70 T5 Emarald Green Metallic, 2004 V70 2.5T Ruby Red, Previous Owner of Black '94 850 Turbo Wagon

there was a problem with c70's having knock sensor codes and poor performance due to retarted ignition timming as a result. this was traced back to faulty ecu's which had to be replaced as the fault was internal. it affected the earlier engine (such as yours) but i cant remember if the service bulletin mentioned 850's or not. however if you have checked the wiring and replaced the sensor then it probably is an ecu anyway. good luck.
steve.