OK, this is a puzzler.
The CEL is on in my 1995 850 (non-turbo). It comes on about 5 seconds after the car is started and remains on. There are NO codes. The only blink code is the "I'm OK and there are no other codes" code. My OBD scanner shows no codes or pending codes. Pretty sure it's not the gas cap, FWIW.
I've seen lots of odd automotive things, but never a CEL with no codes!
Any ideas?
JRE
The CEL is just a powered bulb grounded through the PCM. While there are DTC's which will not show up on a generic code reader or in the blink sequence, they are pretty much limited to internal PCM logic issues. Your Volvo dealer can extract them if you're curious. More likely you have a ground fault somewhere in the dash circuits.
This turned out to be a transmission code. No clue why my scanner and the blink codes wouldn't show it, since it's a generic OBDII code. P0715, transmission speed sensor. The code's reset for now and I'll plan to do the resistance check this weekend.
-- JRE
The reason is that the OBD2 reader just reads the engine control module so as in your case the DTC was set in the transmission control module as the other poster stated the dealer is able to read out all systems in the car with the Volvo System Tester (VST) this is made to read all systems
I have a similar issue on my 1995 850, the CEL light is stuck on and my code reader doesn't show any code consistently. Occasionally I get a P0755 to come out (something about a transmission selenoid) but then it goes away.
Let me know what you find.
Mark
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