Remembering why I
dislike working on
AO Silver Member
Join Date: Sep 2001
OK, just had a look on my car. Looking from the front, facing the back. Lefthand fuseholder is blue, 15A fuse, normal relay, feeds fuel pump. Middle fuseholder is brown, 7.5A fuse, normal relay, feeds lambda heater. Right hand fuseholder is pink, 3A fuse, relay with red stripe, feeds ECU.
Other things to look for if you don't find it's the fuse would be dirty/corroded terminals on the relay socket, fuseholder and also the probe heater 2-way AMP connector. Also make sure that none of the connections has 'pushed back' into the plastic moulding, preventing proper contact. Might also be worth checking that the probe wiring is undamaged.
The 'problem' fuse on mine was physically broken (rather than electrically blown) to one side of the viewing window which meant you couldn't see the break and that if the two parts were in the right place, you got a circuit. Every time I tested it with a DVM, it bleeped as I moved the probes. I mistakenly took this to mean that the fuse was fine and that I was just getting a poor connection on the probes. On numberous occasions when I tested the voltage feed at the lambda connector, it was OK. I only found the fault because it got bad enough that I could see that the lambda wasn't working properly (by measuring the volts from the probe with a DVM). As soon as I saw this, I again tested the feed to the heater and this time it was absent. Took seconds to swap the fuse, see the volts, then about 20 seconds after that, the heater did it's thing, the lambda got hot and started to read as it should. Solved after 2 years of p#@#ing about.
The symptoms your car displays are EXACTLY the same mine did. I replaced probes, I cleaned out the PCV, looked for air leaks, tested every single cable in the ECU loom from end to end, removed the exhaust and repaired a pinhole in the collector by the probe that had been there from manufacture, swapped ECU & AFM, measured every sensor and sender. Never found a thing wrong with any of it.
Keep us posted.