A couple of weeks ago I replaced the water pump gasket in a 95 Z28 . Right after that the check engine light was on it had troubles starting and my cooling fans are running full blast all the time. I checked my code and it was 15 (coolant sensor is too low). Naturally i replaced the sensor. that didnt fix it. someone told me to try the thermostat and even though i was pretty positive that couldnt be the problem i tried it. Nothing. The water pumps working and everything else seems to be in order. It runs just fine, maybe a little rich due to the computer not knowing whats going on (i guess). I'm not looking forward to taking the harness apart to check the wires as they should be fine. So does anyone else have any suggestions on what else to check? Or does anyone think its the computer going bad?

did you bleed the air out of the system when you replaced the wp gasket? F body radiators are lower than the engine so must be bleed whenever coolant system is broken into. Air in system can cause all sorts of cooling problems.

the connector that plugs into the coolant sensor could be corroided

Yeah, I sure enough did bleed the system. I did it as good as i could. There isnt any air coming out of either of the bleeder screws, so if theres a bubble stuck somewhere else i dont know. And i checked the plug the best i could it look just fine. I was thinking about taking it to a dealership to have them look at it. Hopefully they can give me some input instead of crap.

do any of the wires have a kink in them or show signs of expansion? in the morning ill go down to look for this print out my mechanic gave me he also told me they sometime corrode inside the connector so you wont be able to see he used a voltmeter i think it looked like a scientific calculator and he used the printout to tell if the connections had the proper reading

Sorry you think the input is crap asshole,but you never stated in your post that you bled the system, and me thinkng you were another novice, gave a quick answer.

Hey cocobolo, sorry for the miscommunication, I wasnt saying your answer was crap. Chill out. I was saying that i hope the dealership doesnt give me a crap answer and just blow me off like some of my other experiences i've had with letting some one else do my work. No my friend, as a matter of fact your answer was completely acceptable and good advice. But i've already done that. I'm sure you know how some other shops can be... And as for SEDCSS, I can only hope it's somewhere in that connector cause if the computer goes then quite possibly my motor goes.

I'm sorry for my quick temper, but I've had some problems with some of the people on the forum, that think they know everything but actually know little. I like to think out ideas and sometimes they hit the mark and sometimes they miss. I don't know everything about these cars but I'm trying to learn. I will continue to think about your problem and post if I have any answers. One thing the low coolant light gives many people problems. Once again my sincerest apology for jumping on you. Robert Gerard

I have a 95 z28 and the low coollant light came on it but never set off a check engine light I simply unplugged the connector on the radiator. Go figure?

Here is a procedure from shoebox to test out the WP sensor and the wiring from the PCM. You will need a digital multimeter to measure ohms across the sensor and voltage from the PCM. The DTC 15 is saying the referance voltage from the PCM (+5v on yellow wire) is not being pulled down enough by the sensor, it is to high and indicates -56*F for over 2 seconds (open sensor, wire , or bad ground on blk wire). The yellow wire should read +5v from the PCM at the connector with key on and NOT attached to the sensor and when plugged back into the sensor it should read about 1.5-2.0V with the engine at 185-200* F. Black wire should always read 0V and go to ground in either case. Do the resistance check of the sensor first as it's the easiest, then check +5 and ground on the connector from the PCM. If you need info on wire routing in the harness or PCM info let us know... http://shbox.com/1/4th_gen_tech2.html#ect

Two things:

I was trying to find the trouble shooting procedure for your problem in my Factory Service Manual but I need the specific code number that was set, and

How did you go about bleeding air from the system after changing the water pump?

Jake

15 Is actually the code. Thats all that shows up. i bled the system by opening the bleed screws and filling the system, then i closed the screws when it came out and filled it the rest of the way. I'm pretty positive i did it right but of course what can i do right on this car?

I have a 95 z28 and the low coollant light came on it but never set off a check engine light I simply unplugged the connector on the radiator. Go figure?

That has absolutely nothing to do with what is being discussed in this thread. The two things are not related. The low coolant lamp is not connected to the computer.

15 Is actually the code. Thats all that shows up. i bled the system by opening the bleed screws and filling the system, then i closed the screws when it came out and filled it the rest of the way. I'm pretty positive i did it right but of course what can i do right on this car?

Quit screwing around trying to bleed the system. Your problem is electrical and can be easily determined by following what bobdec posted.

Yeah i wasnt gonna mess with the bleeding the system. I'm gonna try and test it at work tomorrow. :mad: I hate messing around with wiring. such a pain in the ass to me.

Ok, so i ran the test's and my results on the black wire are 30 ohms, which means its open, and i couldnt get an ohms reading on the yellow wire. other than that the voltage checked out fine and the sensor is fine. So what are my possiblities? the wires burned, broke or kinked? or they just came loose from the pcm?

Can anyone help tell me where that black wire is grounded at? I guess i'll make sure thats not loose before i open up the harness. I just can't imagine how it would of hurt it. We were gentle as could be takin it off when i did the wp.

I'm not sure about your wire in ?. As I haven't looked at the diagrams to check it out. I will say take a look at the prongs on the connector. I have seen them get bent along with a break down in the connector. Where the wires show voltage but the prongs do not. So check the plug then probe the wires up from the connector.

Well excuse me... Ithought maroz28 said coollant sensor is low in his original post I would think that Was the sensor in the radiator which I knew doesn't affect the check engine light at least in mine. I guess I shoulda known we were talking about a temp. sensor. I'm sorry!

Larry

Dont worry, i did say "coolant sensor is too low". Thats what the scanners say when it reads that code. It's in reference to the voltage though.

Maro.. here we go.... the black wire goes to a splice in the harness that is located 18 cm (about 71/2 inches) from the PCM breakout there are 5 black wires in the splice. One goes to MAP sensor pin A, one goes to A/C pressure sensor pin A, one goes to A/C evap temp sensor pin C, one goes to PCM pin B-16 (actual ground source) and the final one goes to the IAT pin A. I would verify the MAP & A/C pressure sensor black wires are 0v with key on and with key off 0 ohms to PCM reference ground and 0 ohms to each other. If they are OK then rather than tear the harness apart just jumper the IAT ground wire to the MAP or A/C pressure switch ground wire and see if the DTC 15 clears. Then you can decide how to permanently fix it, tear the harness apart, or a permanent jumper install and cut the old black at the IAT end. ALSO (For info only), even though it checked out the +5v yellow wire goes from the IAT directly to the PCM pin C-21, no connectors or splices in that path. (By the way I'm not logged on every day so PM me if you nee more info and I'll tyr to assist... Bob D)