A little while back I got a SES light on my '90 and it was a code 15. I checked the coolant sensor and the plastic around the prongs was broken and it was unplugged. I put the connector from the harness on it and electrical taped it in place to make sure that was the problem. I drove it around for a bit and never got a light. I replaced the sensor with a new one and on my first trip around the block I got a SES light and again code 15. I disconnected the battery to reset the ECM and then drove it again. There were no lights at first but now it is back with a code 15. Could it be that the part store just sold me a bad sensor? Or is it something else?

Also, I dont know if the two are related, sometimes at idle the RPM will jump up to 1500-2000 and stay there. Sometimes it will go up and come right back down and sometimes it will be perfectly normal. I added headers and duel exhaust and had the chip programed. None of this happened with the other tune and the previous mods. Might I have a chip issue?

Thanks in advance!

 

Anyone??

 

I guess I could try a new sensor, they are pretty cheap, but I dont want to be one of those people who replace things without problem solving. Any tips on what I should look into at least?

 

bump for some help

 

Your code 15, low coolant, can sometimes be a little hard to diagnose.

First - you should check out and replace the low coolant sensor. Yours is most likely the original part and as they age the plastic housing tends to get brittle and can crack. The part is only $20 and is easy to replace. Ecklers has them available http://www.ecklers.com/product.asp?p...2&dept_id=1309.

Second - make sure you check out the sensor wiring.

Third - Make sure that you have properly burped your radiator as air trapped under the thermostat can cause air pockets and can throw a code 15 low coolant alarm. Carefully read the attached burping instructions that I have included for you.

Finally - If you do all of this and you are still throwing a code 15, carefully and diligently check ALL of your heater and radiator hoses. While you might not think so, a small pin hole in a heater hose once kept me guessing on a code 15 for over 14 months. The problem turned out to be a very, very small pin hole in the underside of a remote heater hose. Once the leak was fixed my code 15 problems were finally solves.

Check it out and let us know how you make out.

Good luck

 

Thanks! That sounds like a good place to start. I have already replaced the sensor but will look into everything else.

 

Anyone know what could be wrong with my idle?

 

Your IAC can be either dirty or faulty and in need of replacement.

 

To clean it what can I use and how is it done? When the car is cold it doesnt like to idle and sputters when I give it gas. I take it this could be the IAC as well?

 

Another question, If the IAC is bad will it throw a code or just idle/run poor?

 

You can reset your idle speed and IAC and then adjust the TPS and make sure its set correctly. Also check your ignition timing with the EST wire unplugged.

 

Thanks. I will check those things as soon as I can get my hands on a voltmeter. The timing was set not that long ago the correct way. I thought the idle problem could be part of the code 15 but it sounds like more of a IAC problem.

 

90 has NON-Adjustable TPS, although you can check its output w/ a digital volt meter to confirm it is in range.

SES, is that showing up in the speedo/info area? That is sometimes just a low voltage indicator. Your idle is a little low, battery &/or alternator weak...

 

The SES light shows up in the center counsel above the radio. When I start the car after it has been sitting a couple days, it struggles to stay running until it warms up. When its running normal and I am at a stop light or just stopped, sometimes the idle goes up to 1500-2000 RPM and stays there. How can I check the IAC to see if its ok?

If the TPS is out of range does that mean it is bad?

 

Ok so I burped the coolant and it seems ok, but the SES light it still on. Should I disconnect the battery again?

I have not had a chance to look at the IAC but I found thread where someone said in order to reset it I should unplug it, start the car let it run, shut it off, and plug it back in. I did that but dont really notice a difference. I think the idle could be from the code 15. Any other suggestions on how to remove it? The connectors and wiring look fine.