Code 15 headache

[wheels87k5]

Please understand that my K5 is possessed. And since I was born on Friday the 13th, we go together well.

Started the truck this morning to let it warm up....let it run for about 5 minutes....came out to leave, and it was revving a bit higher than normal....would calm down for a sec or two, then rev higher again for a few secs....repeat.
I got in to leave and as soon as I put it in R, it boggled and died. I tried starting it, and it would only try to actually start with the pedal to the floor.....boggle and die.
Got out, went into the house for a couple minutes, came back out and it started right up and ran fine all the way to work.

This isn't the only episode.....it's acted similar to this shortly after starting it and driving about a block before it did the same thing as above.

It gives me a code 15.

I've gotten this code also while driving down the highway at 70 mph. The check engine light will come on for about a minute then go out.

When I head out to work, and it's running fine, I feel a surge of "get up and go" as I'm taking off to get up to speed for the highway.

My temp, oil pressure, and battery gauges read higher than normal. EX: temp gauge will read 210 and the actual temp is 192. Oil gauge stays at or past 60 (almost pegged), and battery is between 13 and 18. All gauges have been swapped with known working ones.

I did a winadl test and compared to what I've seen from other owners, mine is screwed up. I don't know how to put it in a zip file to send to the site that's recommended on here.

I checked the ground straps and they are good......Can the alternator cause this?

I may have to chase the wiring down to see if there is something shorting out or grounding.

These episodes only happen about twice a month.

Just wanted some input on possible causes. And like I said before, it's possessed.

 

[dyeager535]

http://www.thirdgen.org/techboard/t...45-help-im-shooting-bunch.html?highlight=code

Two pages of Code 15. Nice to know what is going on, why it's triggered, etc. Relatively simple circuit.

If your volt gauge is reading high, what does winALDL say? I'd trust it as much as a voltmeter, but I wouldn't hesitate to put my voltmeter on the back of the alternator. If the problem is intermittent, take a voltmeter with you and test as soon as you see the problem.

 

[wheels87k5]

Thanks, Dorian.....I appreciate all the help from you and anyone else.

You've helped me more than once.

The reason I ask about the alternator.......when I bought it, the mounting holes didn't match the brackets on the engine. The tech at Advance Auto had to take it and clock it so it would fit right. They didn't have one in stock (with the correct mounting holes) and told me that clocking the one they had in stock would not hurt anything.

Makes me wonder now.

But I have "sometimers" syndrome and can't recall if it did happen at about the time I bought the new one or before.

 

[dyeager535]

I had to clock mine as well, *shouldn't* hurt anything, but I also just posted that I had my alternator crank the voltage up to 18volts for no reason, so dunno. Shouldn't have any effect on the voltage regulator, everything is fixed to the rear housing AFAIK, but I've not had the CS-130 apart all the way.

You running a CS-130 or 12-SI? Not sure when they went to the CS-130, may have been later than the '87's.

Definitely something to check though. My ECM will throw a code with too much voltage, and it affects how the vehicle runs, but shouldn't throw a CTS code. Voltage being too high is much more serious than a failed CTS though, so figure that out first.

 

[Thunder]

Re code 15.
IMO you are barking up the wrong tree worryng about the alternator. Code 15 is a problem with your Coolant temp sensor. Not alternator. the CTS is suplied with 5 volts. Alt output has nothing to do with it.
I would replace the CTS and check the wires and plug for shorts before doing anything else.
BTW. The code for system overvoltage or Alternator being out of range is 53

 

[wheels87k5]

I respliced a better plug-in for the CTS because the old one looked like the wires were pinched at the point where they enter the top of the plug.

Rechecked all grounds and realized the firewall to engine ground strap was connected to the header bolt near the firewall. I moved it to the back of the head.

You're right Thunder....Alt checked out good so it should'nt be the problem. But I'd like to find out why the oil pressure and temp gauge read higher than they should.

I swapped a good working oil pressure gauge from a buddy's K5, and it still reads max pressure when it's warmed up and at highway speeds. When it's in his K5 it reads about 40-45 at highway speeds.

Same with water temp gauge.....swapped it out with a good working one and it reads high, about 210 temp when it's actually 192-195.

What would cause the false reading on the gauges?

 

[dyeager535]

If the voltage/alternator checks out, I'd be thinking the connections on the back of the instrument panel. Wouldn't hurt to check/swap the fuse for the gauge panel first though, it's easy. Just had one break apart on me in the socket, can definitely see a poor connection there causing problems as well.