1991 Bonneville no overdrive, code 39.
My Bonneville has just over 100,000 on it. A few months ago the overdrive would stop kicking in at cruising speeds. Sometimes it worked, sometimes it didn't. When this happens there is no noticeable sign other than the cel comes on and the rpms go up.
When it kicks in, the cel goes out and the rpms come back down. Now it doesnt go into overdrive at all and the cel stays on all the time. I pulled the code and it gave 39 tcc switch.
I have read several forums about the tcc switch but they all describe it as if its the tcc solenoid there will be shakes, shudders, or starting/stopping issues. I have none of the issues. The Bonneville runs fine other than my overdrive doesn't kick in.
I'm wondering if this is a bad wire issue and something else.