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Greg A
Greg A, Master Troubleshooter
Category: Chevy
Satisfied Customers: 5975
Experience:  Working with Electronics & Cars for 25+ Years
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1999 Yukon: What it it telling us is wrong

Customer Question

My 1999 Yukon park indicator light stays on all the time. What it it telling us is wrong?
Submitted: 5 years ago.
Category: Chevy
Expert:  Greg A replied 5 years ago.

Hi Danny,

 

I have the documents that will give you a start on troubleshooting this problem. The following is a PDF file that you should be able to view on your computer and print.

 

Parking Brake Light Always On

 

Here is the description of the system, and the schematic that goes along with it.

 

graphic

 

graphic

 

Please let me know if you have more questions.

 

Take Care, Greg A.

Customer: replied 5 years ago.

Greg,

 

I have started the troubleshooting process from the pdf file you supplied. I disconnected the parking brake wire switch and the indicator light stayed on. The next step says to check for a short in PPL/WHT in wiring system, how do I go about this?

 

Also the check engine light came on, service engine soon. I have recently replace the sending unit servo harness in the tranny for $450 thinking that was the problem. The other day the engine stuttered at idle take off stalling and I had to pump the gas to get the yukon to move forward and run.

 

I found the vacuum line cracked to the pcv or pvc valve and fixed that today.

 

I will accept your answer when the light goes out. So how do I check for the short in the ppl/wht?

Customer: replied 5 years ago.

Greg,

 

I just went out and started the yukon. Put the park brake on the the drl module kicked off the lights. Working like it should. So if the purple and white wire are shorted to ground would the drl module still work?

Expert:  Greg A replied 5 years ago.

Hi again. Sorry for the delay - I had to run a couple of errands.

 

The Parking Brake switch normally tells the DRL system NOT to turn on the lights until the parking brake is released. That is what the purple & white wire is supposed to do when the parking brake is engaged. That is, it will connect the purple & white wire to frame ground.

 

Now if the wire is shorted to ground somewhere between the parking brake switch and the DRL module, then the DRLs will stay OFF, but you would also have that Parking Brake Warning Light stuck ON, which is what you had when we started.

 

What I don't know is what "Put the park brake on the drl module kicked off the lights." means.

 

So if the purple & white wire is shorted to ground, then the DRLs should stay OFF. If the wire was OPEN (or not connected to the parking brake switch) then the DRLs would turn ON immediately, when the vehicle is started (assuming it is daytime).

 

My Chevy van works in this same way - DRLs stay OFF until the parking brake is released.

 

Please let me know if that helps or if you still have an issue related to the lights.

 

Thanks, XXXXX XXXXX

 

P.S. To check for a short to ground, I would use an ohmmeter set to the Ohms scale. Then connected one test lead to a good frame ground, and touch the other test lead to the contact of the wire. If it reads about 2 ohms or less, I would consider that a short to ground. The wire should be disconnected from the parking brake switch at the time of the test.

Customer: replied 5 years ago.

Greg, sorry for the confusion.

 

I started the yukon. The drl were on. I engaged the parking brake and they went off. So the drl is working ok.

 

I disconnected the wire to the brake switch and the light remain on.

 

I did an ohms check like you said and it show nothing. I used one lead to a good ground and the other to the connector from the brake switch.

 

Now what should I try?

 

The light is still on.

Expert:  Greg A replied 5 years ago.

When you say you found "nothing", I am assuming that means that you did NOT find a short (0-2 ohms).

 

If that is the case, it is time to move to step 4 of the test procedure. Let me know if you need help with that.

Customer: replied 5 years ago.
Greg, where is the disconnect for the drl module? This seems to be a lot of trouble to make a park indicator light go out. What will happen if we just let the darn thing burn out? Maybe it will never burn out being of a light diode. Will it drain the battery? Do you know how much draw it has? What would be the worst case senerio?
Expert:  Greg A replied 5 years ago.

Hi again,

 

The Daytime Running Lamps (DRL) Module is located under the left side of the IP (Instrument Panel), taped to the IP harness, as shown in the diagram below.

 

graphic

 

I agree that it can seem like a lot of work to debug a problem in an electrical system, especially when electronic parts are concerned. This is the disadvantage to "advanced" control systems - I like "simple" circuits where individual components can be tested and replaced as needed.

 

If the light burns out, you would have no indication that the parking brake is stuck on (if it actually is some day), and you could heat up the brakes. If it is an actual LED, it would draw very little power and may not burn out for years. But the schematic uses a symbol that indicates it is a "regular" bulb, so it will draw more power and it could drain the battery after several days or more without starting the vehicle. I do not have the current rating for that particular bulb, so it would be hard to say how long this would take. Worst case - the battery would be drained repeatedly and you would have to replace the battery more often than expected.

 

Now - after looking at this some more, and seeing a picture of the connector for the DRL module (below), I am kind of starting to suspect the DRL module itself, or maybe some of the pins are shorted at the connector.

 

graphic

 

graphic

 

 

What you could do is isolate Pin E, which should be supplying the "Ground Path" for that bulb (according to the schematic). You can isolate this pin by placing Scotch tape over the contact with pin E and see if the light goes out. You should be able to do this because the DRL module is supposed to be a little "PC Board" that plugs into the connector. Make sure the tape only covers pin E.

 

What I have done in the past is to place the tape on the PC board, and then trim it with a razor knife so that it only covers the contact that I want to disconnect. Then carefully plug the module back in, so that the tape stays in place, and see if the light is out. If so, the DRL module may be shorted in that area.

 

I priced the DRL module (probably dealer only part) and it is about $65 (USA version). Kind of pricey, but it is a "special" part, and if it fixes your issue, it would be less than having to take the vehicle to a dealer to fix it. OR, you could just leave the tape in place to keep the light off, but then you would not know if the parking brake is ever left on.

 

Please let me know what you find, and what you decide to do.

 

Take Care, Greg A.

Customer: replied 5 years ago.

Greg,

 

Maybe we are not talking about the same indicator. There is a parking brake light up in the right hand corner of the instrument panel that comes on when the parking brake is engaged. It goes off when the parking brake is disengaged.

 

The indicator light I am talking about is the red line indicator for what gear your in, ie. park, reverse, netural and drive gears.

 

That little line is bright on all the time, even when the ignition is turned off.

Expert:  Greg A replied 5 years ago.

Hi again.

 

You are correct - I did not understand which indicator you were referring to. Please accept my apology for that.

 

Can you tell me if the indicator shows the proper selection (Reverse, Drive, etc.) when you select those positions?

 

Does the Park indicator turn OFF when the other postions are used, or does it stay on ALL the time?

 

Thanks

Customer: replied 5 years ago.

Dear Greg,

 

The indicator stay bright lit all the time. It moves with the selected gear.

 

It stays on even when the ignition is turned off. I have disconnected the battery several time to reset the computer and the check engine light goes off for about 4 or 5 days.

 

I had a PO740 code that told me the tranny needed serviced so I spent almost $500 to fix the soinoid harness with fluid and filter change.

 

Does the indicator light have anything to do with the tranny?

Expert:  Greg A replied 5 years ago.

OK - thanks for that information. Yes - the indicator light does have something to do with the transmission. More precisely, it has to do with the Transmission Range Switch, which is part of the Park Neutral Position (PNP) switch mounted on the transmission. Where this switch is depends on which transmission you have (see diagrams below).

 

Here is the schematic for that system.

 

graphic

Switch Position for the 4L60E transmission:

 

graphic

Switch position for the 4L80E transmission:

 

graphic

 

What you can do is follow the procedures below to remove the C2 connector from the switch, and then tie fused jumper wires to ground and the appropriate cavities in that connector. Below is a PDF version of the test chart for this particular issue.

 

PRNDL Inoperative Chart

 

Here is the procedure they refer to in step 2.

 

graphic

Here is what Connector C2 looks like, and the pin assignments. This also includes the wire colors going to this connector.

 

graphic

 

Now, if you just had the harness replaced, and this problem started right after the harness was replaced, there may have been some "rewiring" done at that time. Make sure to check the wire colors and see if they match.

 

If the colors do not match what is above at that connector (C2), then I would "have a conversation" with the folks that did the work and ask them what happened or if they check this function after the work was done.

 

Please let me know what you find, or if you have more questions.

 

Take Care, Greg A.

Customer: replied 5 years ago.

Greg,

 

I am sorry for the delay. My motorhome broke down with the horse trailer on Thursday and I had to run 200 miles to rescue my wife, daughter and the horse. It took until today to get it back home.

 

The yukon is away pulling the trailer with one horse. The total weight is around 6k. I hope the tranny holds up with that light on. The town car broke down last Wednesday, the motorhome on Thursday and My dually crewcab busted a hose today. So all three is a charm and the yukon should not break down right????

 

Al I can do at this time is wait for them to return on Monday and sometime next week I should have time between jobs to start the test you have supplied for me. I need all the luck I can get at this time. If I accept you answer right now will I still be able to view all links you have supplied me?

 

Thanks in advance.

 

michael

Expert:  Greg A replied 5 years ago.

Hi Michael,

 

Sorry to hear about all the bad turns of fate with your vehicles. But if everyone is safe and sound, that's what counts.

 

I am in no hurry. If the system here sent you a message, it is because I go through my list of questions every few days to send messages to check up on folks.

 

You can accept now, if you want to, and you can continue to return here for some time to check the responses. You can even re-open the thread in the future, or ask a new question if you want to. Or you can leave it as it is, and we can continue where you are ready. The choice is yours.

 

Take Care & Stay Safe, Greg A.

Customer: replied 5 years ago.

Greg,

 

Thank you very much for your reply.

 

So the light remaining on and the yukon running in perfect condition and the tranny opperating normal is not an alarm? Just a selector switch indication? I have not had time to read the threads or links.

Expert:  Greg A replied 5 years ago.

Hi again,

 

I think you are probably OK, as long as the Yukon is working alright.

When you mentioned the wiring harness for the transmission, that is what makes me think that it may be the range switch, or the connector to it. It could be a simple adjustment. Once you get a chance to have that connector checked out, that should tell us what is happening.

 

Let me know what happens when you get to it.

 

Take Care, Greg A.

Greg A, Master Troubleshooter
Category: Chevy
Satisfied Customers: 5975
Experience: Working with Electronics & Cars for 25+ Years
Greg A and other Chevy Specialists are ready to help you
Customer: replied 5 years ago.

Thanks Greg,

 

My wife called and said the service engine soon light just came on again but everything seems to be operating fine. She is down in Parker Co. and I hope I don't have to drive down there again to rescue her. She is about 250 miles away from home.

 

 

 

 

Expert:  Greg A replied 5 years ago.

Is this in the Yukon?

 

You could ask you wife to stop by an auto parts store where they read the codes from no cost, to find out why the light is on. Could be just that the gas cap is loose after the last fill-up.

 

If you decide to do this, have her write down the code and you can give it to me here, to see what the light was caused by.

 

Thanks, XXXXX

Customer: replied 5 years ago.

Greg, sorry it has taken me so long to get back to you. I still have not found a code problem with the check engine light.

 

I disconnected the postions sensors wirning harness and the light stayed on.

 

I give up. I have spent more time on this little indicator light than one should.

 

Thanks again,

 

Michael

 

Henry, NE

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