Hi guys.

My service engine soon light has been going on and off intermittantly. Lately, it's been more on than off.

I changed the oxygen sensor--no fix.
So I brought it to the local mechanic, who told me that even when the engine was starting from cold, it's throwing a code 14--high temp at engine coolant temp sensor.

Long story short: he replaced the coolant temp sensor. He's saying that he now thinks the computer's fried, and that the switch that I attached that grounds out the fan relays (so I could switch the fans on whenever I want) probably did it. I've had that switch in for a year, and have used it occasionally, with no problems. He also said the Bosch 02 sensor I installed could cause problems (it's only been in for a few days).

Is his bad CPU diagnosis reasonable?
Is the fan switch (I wired it from info from this board) really a threat?
Should only an ACDelco 02 sensor be used?

Thanks.

 

Unhook the negative battery cable and leave it disconnected 24 hours to clear out teh non-volitile memory in the computer. Drive the car again and see if the SES illuminates. If it does, use teh paperclip in the ALDL to retrieve teh code. It wont be conclusive proof of a problem, but at least youll have a direction to head in.

The O2 shouldnt influence the coolant sensor. The fan switch could if the fan isnt coming on. It really could be getting so hot that it causes a code to be set. If the CTS was replaced but it still gives code 14's, you can easily check teh continuity with a DVM. At KOEO, disconnect the CTS and measure the voltage across teh connector. It should have +5 volts. If not, there is a break in the wiring somewhere.

 

Thanks, dimented24x7.

I have the car back. It's true that the cts was bad. So I'll have to search the wiring.

Also, the heater core just started leaking. Any possibility that could be shorting the wire out? I'll probably do the heater core bypass thing tomorrow anyway, so I guess I'll find out.

 

My manual fan switch was wired that way for years with no problems. There is no way that damaged your ECM.

 

umm, hows your rad cap. if its not the proper one or if your low on coolant, its not hard for you to get that code. if you find the problem and fix it, replace that heater core fast, or take it out now and bypass it until you fix it.

usually its best to rule out the cheap and obivous things before you go spend money on electronics and modules that may or may not work.