'89 K5 won't shut off

[extra_230s]

So, I'll just start at the beginning...

A couple weeks ago everything was normal, then I parked it for a week or so before I tried to start it up. After trying to start it and there was no juice, the battery was dead. I took the battery out and charged it, then I installed it back it the truck. Right before I turned the key on I noticed the "service engine soon" light was illuminated which I thought was odd seeing as how the ignition was turned off.

Well then I proceeded to start it up and it ran smoothly. Then I turned the key to off and the truck kept running so I stalled it out. I noticed while the ignition is off, that the "service engine soon" light stays on continuously. Honestly I figured it was my key ignition barrel switch seeing as how I have never needed a key to start it up, so I swapped it out and it still will not shut off. Next I proceeded to swap out the ignition switch mounted on the column in the dash, and still will not shut off. Have any of you guys experienced this issue? Certainly is odd to me and I'm kind of at a loss. Any help will be appreciated.

Also just so you know what I'm working with, it is a 1989 K5 with a TBI 350, and I swapped out the 700R4 with a NV4500 last year. Thanks!

 

[dyeager535]

Was this a brand new problem with the battery swap, or did you just notice that the SES was illuminated all the time, and that's why the battery died?

I'd have to look at the wiring schematics, but the SES light means the ECM is getting power. That's dumbed down a bit, I believe the ECM is powered from two wires, one constant, one ignition switched, but I think you understand what I mean...it's getting power on the switched side when it should not.

I can't think of anything that logically would allow the ECM to have power with the key off...if you pull both ECM fuses, does the light go off?

 

[extra_230s]

I'm thinking the battery died because the SES light is on continuously.

I will have to try pulling the fuses first chance I get to see if it will shut off.

 

[nutt7]

Do your other accessories stay on when you turn off the ignition? Based on what stays alive, we can locate where the issue is coming from. I have factory schematics for an 89 burb. Should be the same in the effected area. Let me know if you need a pic.

I would guess that something after the ignition switch is shorting with a 12v constant causing it to keep some circuits alive...or a relay is staying closed. Like dyeager said, check the fuses. The short I speak of may even be happening in the ECM.

 

[extra_230s]

Alright, so I had some extra time today to diagnose a little bit further. You are right nutt7, there are more accessories that stay on. Here are the accessories that are continuously when the ignition switch is off, also see the first photo below for reference:

• The SES light
• The Brake light when the emergency brake is pressed down
• The radio
• And the AC/heat/defrost switch bank (but not the blower)

Now, I had taken out the ECM fuse and the only thing it turned off was the SES light. I have looked all over for my shop manual so I can find a schematic but had no luck. I will have more time this weekend to further diagnose, any ideas or remedies are greatly appreciated, thanks for the help guys!

 

[dyeager535]

Did you adjust the ignition switch properly? Outside of some butchered wiring, the indications are that the ignition switch is in the "run" position.

Not a real easy task as I recall, but if you unplug the wiring from/to the ignition switch, I bet it all turns off.

 

[extra_230s]

I'm guessing it is adjusted correctly because I did the same thing with the old ignition switch and key barrel.

 

[extra_230s]

It did**....

I will check into that later on this week once I get back from out of town. Thanks dyeager535

 

[dyeager535]

Probably not real likely, and I have no idea how you'd tell if it was, but maybe the rod that actuates the ignition switch has been straightened or something weird?

All indications for some reason the ignition switch is in the run position, mal-adjusted switch or rod being too long are the only things I can think of. Don't know as the lock cylinder can be installed incorrectly or have an issue that would allow the key to physically be in the "off" position yet somehow still rotate the linkage forward like it's in run.

 

[extra_230s]

I understand what your saying, but it is hard to believe that would be the case seeing how it was fine when I parked it... Then 2 weeks later I have this.

 

[dyeager535]

I understand what your saying, but it is hard to believe that would be the case seeing how it was fine when I parked it... Then 2 weeks later I have this.

To start randomly I agree, and to have both switches have same issue, also way too coincidental. The cluster is getting power though, among other things (ECM, brake switch) so something is up, and it's all going through the fuse panel/ignition switch. I can't think of one thing that could cause all that, that is likely from just sitting.

 

[nutt7]

I have a couple questions: which ECM fuse did you pull? ECM1 (sw) or ECMb (constant)? How is the radio powered? What color wires on the truck side? I know sometimes people tap different wires for this. What do you mean about the ac, heat, and defrost bank working? The blower is powered on the same wire/fuse. Have you ever messed with those jumper terminals above the fuses? Knowing these can help isolate the issue.

Looking at my diagrams, the SES light and BRAKE indicator are supplied a 12v switched from a pink/black wire (39) coming off the GAUGE/IDLE fuse. The brake negative comes from the park brake switch. The negative to the SES comes from the ECM. I believe this signal is always there until the ignition is turned on and things get going and the ECM removes the ground signal. The common link seems to be the pink/black wire getting power when it shouldn't. The process below shows how I would chase down this aspect (disregarding the radio and climate control part that I don't understand yet):

Pull the GAUGE/IDLE 20a fuse.

Do all the accessories turn off (SES might have a delay)?

1) If yes, put the fuse back in and check the pink wire off the ignition switch. It seems to run to the ignition coil, powers the ECM1, IGN, GAUGE/IDLE, and TURN/BU fuses. Unplug it at the ignition switch. (Btw, do the turn signals work without the key turned? If no, we might want to pause before proceeding.)
Do the accessories turn off?
a) Yes -> check continuity on ignition switch from where the red wire goes to where the pink wire goes (tumbler in "off" position). Continuity? If yes, ignition switch problem. If no, turn key to run to verify continuity (should be good...check for good measure...or maybe all of them for proper function). Plug it back in.
b) No -> something is shorting 12v to the pink wire. Pull these fuses one by one and check if problem persists: ECM1, IGN, TURN/BU. If problem goes away, let me know and we can go down that route. If pulling a single fuse doesn't eliminate ALL problems, pull the plug with the pink and white wires at the coil. If problem persists, it seems the short is somewhere in the pink wire. If the problem goes away at this step, there is a problem in the ignition module or ECM (unlikely).

2) If no, there exists a short in your pink/black wire 39 coming off the GAUGE/IDLE fuse somewhere. It's a bear because it splices out and supplies 12v switched to lots of things. Like dash indicators, alternator exciter (varies), etc. if this is the case, we can go that route too. Let me know. If you want to troubleshoot this, make sure you pull the fuse mentioned first.

 

[JOES89K5]

Hello I know this is an old thread but did you finally find and solve the problem.

 

[trukman1]

I'm wondering the same thing as JOES89K5...can you tell us what it was in case someone else runs into the same situation?