I am getting a code 15 and i already had a new CTS on the car and so i checked the connection and it seems fine, and i changed the sensor and i still get it after i reset the battery, i checked the voltage across the terminals and it was 5.v(well 4.97) the car heats up fairly fast and i dont see why, but sometimes the light will go out so im not sure what is going on there. maybe i need to clean up the connector a bit or something. it seems to run alright runs kinda choppy at start up but when it gets a little warmer itll stay running easily. is this possibly a simple connection problem? or is there something else to a code 15?

 

Since you have a new CTS, and have a 5V reference voltage at the sensor, you need to check the ECM edge connectors. You should also check the engine cround strap and grounding connections at the RR of the engine. For some reason, the ECM is seeing too much resistance across the sensor (open circuit).

 

Im not sure what you mean the edge connectors? i think i might run another ground from the engine to body. i think it might be the connection but ill check it when i get my my AFPR from holley, damn crap regulators.

 

The "edge connectors" are the harness connections at the ECM itself. They can become dirty, loose, and oxidized. You can often "freshen up" the connections simply by removing and reconnecting the plugs a few times. The wiping action of the contact leaves or pins over the ECM card edge or header connectors (depending on ECM type) is often enough to clean the dirt and oxidation from the connectors and provide good contact.

Since I'm guessing you have the CCC type ECM, it likely has raw circuit board edge connectors, like this type:

 

oh ok im using a 87 TPI ECM and i changed the harness from one i bought off e-bay, maybe thats it, ill unplug it and plug it in a few times and see what happens. maybe its just my connection at the CTS also.

 

well that wasnt the problem, my engine light goes off and on when im driving and doesnt seem to affect anything really, but lately its been staying on. this is odd. any other troubleshooting?

 

Hrm...book says here to dissconnect CTS and jump the terminals together. Start engine and run for one min or untill SES light comes on and then check code.

If you get code 14, the connection or the sensor is bad

if you get code 15, probe the yellow wire (ckt 410) with voltmeter to ground. It should be 4-6 volts.

If it is 4-6 volts, the sensor ground circuit is open or faulty ECM connection, or bad ECM

If its not, the yellow wire (ckt 410) is open, fault ECM or bad ECM.

 

Pencil eraser is good for cleaning those contact points you can reach. They don't look bad in the pic. Electronics cleaner is good for the ones you can't reach.

 

im going to try this today. thanks for the advice

 

well i jumped it across the wires and i reset my codes and i ran the car up to about 190 i drove it around and everything and the engine light didnt come on at all.

 

ok i checked the codes anyways and it came up with code 14, but iv replaced the sensor a few times already. so the connection must be bad....or do you think i need to put another ground cable in from the engine to the body?

 

I put in a new CTS before I did the cam break-in, 2 weeks later I get a code 15, I do the diagnostics, and don't find anything wrong in the circuits, so I replace the sensor, no more code 15.

 

well i had a new one on there and i changed it and i ended up swaping out the wiring harness and then i had that code. so maybe ill put my other new one in and itll fix the problem.

 

It's a wiring/connector issue of some kind, I'm sure. I had an intermittent code 14 on an old Blazer (CTS reading too high). It wouldn't do it while idling in the driveway but if you accelerated under load it would often pop a code.

Turned out that one of the CTS wires in the harness had chafed against an engine bracket and was intermittently shorting against it, but only when the engine torqued over under load. I pulled it away from the bracket, repaired it, wrapped a little tape around it and never had the problem again. Guess how long it took me to diagnose THAT little bug!

I suspect you are having some sort of similar problem- a broken/chafed/pinched wire somewhere, or the connector itself is bad.

 

now that you mention that, i have the CTS mounted on the drivers side of my HSR and it makes the wire extend to the limit and makes it a little hard to plug in. so maybe if i pull more slack out of the rest of the harness itll be fine.

 

Hi, just curious if you ever solved the problem. I'm having a similar problem with an intermittent code 14. Replaced the sensor, no change. Replaced harness, no change. I guess it must be the connection at the ECM or the wires in between.

 

no actually i havnt figured it out, if i let my car sit over night, there wont be an engine light till like 1 minute of it running. i loosened the wires so they wernt touching the block, i changed the sensor, i might try putting another body to engine ground.

 

Well, I checked the resistance on the cts today and compared it with the resistance/temp chart floating around on the boards. Seemed fine to me, although I only checked it at one temperature (~90F)...1.7k.ohms. I didn't appear to be getting any voltage at all through the connector. I'm gonna check the continuity of the wire and check the computer connection tomorrow. This is getting ridiculous. I probably need a new ECM, knowing my luck. F.

Well let us know if you make any progress with your problem.
--AA

 

yeah i dont have the foggiest, since i already changed the harness i think its probably my engine ground so i have to do that sometime this weekend and see what goes on. let me know how your troubleshoothing ends up.

 

Hey, I ended up replacing my computer, which seems to have solved the problem. I haven't been able to verify this with a scanner yet to make sure the ECM is interpretting the correct temperature, but I have not gotten code 14 since I replaced the computer...been over a week. My car also idles pretty steady and low now which didn't do before.

Here's my thread...don't remember if I gave you this before or if you have looked at it. But, maybe something there will help you if you are still having troubles with yours.

https://www.thirdgen.org/techbb2/sho...hreadid=289744

--AAron

 

let me know when you get it checked out. was you car doing the same thing as mine? bucking at slight throttle and almost nothing at 1/4 or more throttle?

 

A rubber eraser is very good at cleaning connectors.

Connections are the least of the problems on that ECM. Did you notice the upper LH corner of the board, where the smoke was allowed to escape? Easy fix, and common problem on ECMs that have been exposed to overvoltage.

Marrow,

Did you tap-test the ECM? May have a failing solder joint there.

 

no i didnt try that but i think thats what could be the problem. do you think not enough grounds to the engine would make the computer "burn out" because all i had was the stock GM mesh wire ground, and now i have a extra 4 gauge ground wire on the engine to the brake booster. i havnt driven it yet. but i know where a spare computer is if i do the "tap test" on it and nothing comes of it, iv had the problem since i swaped it to fuel injected. ill let you know what happens. or you can fill me in a little