Overdrive Issue?

[wmcvetty]

Odd one for you guys.

Driving at interstate speeds (55mph+) I have noticed an issue where my RPM's spike and I get alot of "engine braking" for lack of a better phrase. Took it to my shop and they flushed everything out for me as I was unsure of the history and I only had 71K on it. They said everything looked good, and could not reproduce the issue before/after the flush. Of course not right?

It happened again today, but I noticed something really freaky.

It seems to only happen either of the front windows are down or if the sunroof is open! Also, it turns my rear defroster light on when it happens? I rolled the window down a couple of inches, it would happen. Rolled it up, it stopped. Tried the same with the back windows, nothing happened. Tilted the sunroof, it happend. Closed it, it stopped. Opened the sunroof, it happend. Closed, stopped. All this was with the headlights on. Thought about the lights after getting of the interstate, but I turned them off and could not get it to reproduce the issue at 55 MPH speeds - will try the interstate on the way home today.

I say overdrive because when it is happening (rear defrost light on and the window down with RPMs spiked) if I press the overdrive button nothing changes like it would normally. But when everything is running normal if I hit the overdrive button the RPMs spike in the same manner as my issue does.

Please tell me I don't have an electrical gremlin.

Thanks guys.

Walter

[WPGQX4]

Did you feed your QX4 after midnight? It sounds like you have an electrical gremlin.

[wmcvetty]

And then splashed him with water....

Trying to figure out the common factors of the front windows and sunroof would have when down, but not up. I cannot think of anything that the car would be monitoring the status of a window being open for, and since it is only happening then it confuses me.

[ARKQX33V6]

Can you determine if the engine speeds up also as the tach does or is it just the tach speeding up?

[wmcvetty]

I'll check on that.

Did a test spin at lunch on the Interstate and found another piece of the puzzle. Seems that my lights have to be on to cause the issue, even if it is just my parking lights. If you have the window down and turn them off there is no issue, but if you turn them on to the third stop the issue occurs. I am fairly sure that my parking lights are not working, I will have to check tonight when it is dark to be 100% sure.

[wmcvetty]

Can you determine if the engine speeds up also as the tach does or is it just the tach speeding up?

How would I determine that? May be a stupid question but the more I thought about it I was unsure.

[Empty V]

If it's revving but not going any faster.

[wmcvetty]

Ok, thought I was over thinking it. No, the car does not go faster. If anything it slows down it seems, almost like you hit the OD button on the gear shifter while doing 70-80. I'll try on the way home to make sure I am telling you right.

[ARKQX33V6]

Can you determine if the engine speeds up also as the tach does or is it just the tach speeding up?

How would I determine that? May be a stupid question but the more I thought about it I was unsure.

-----------------
To determine if the engine is actually speeding up at the same time as the tachometer indicates higher speed:
Listen to the engine,
Try downshifting to increase engine speed, is it normal sounding,
Get another tachometer and relate the car's tach to the test tach,
Measure the alternator voltage at the cigar lighter, does it go higher
Read specific voltages via the ECM

But the easiest is to listen to the motor

[wmcvetty]

I thought that the tachometer measured the RPM's of the motor so how could the RPM's spike but not the engine? Excuse the stupidity on this subject matter.

I definitely hear the engine roar, if all that you are trying to eliminate is a faulty reading from the tach.

[selfguided]

definitely seems like some sort of short in the wiring harness. break out the multimeter and have fun!

[wmcvetty]

you have a sick definition of the word fun my friend.....

[wmcvetty]

Well I avoided this issue as long as I could, and recently it started turning overdrive off if the headlights were on no matter what. That, or if I put it in reverse, turned the rear wiper on, turned the defroster on, or put the car in reverse....

Read the Electrical section of the FSM way more that I ever thought I would, and stared at some schematics for a long time. Started tracing ground wires and found a large amount of repeats for the triggers of my issue, all of which led to the rear hatch. Pulled off the cover to investigate and saw the grounds looked good. Then I noticed a whole harness that was UNPLUGGED! Plugged it in, and all seems to be working now!

Woot!

Had to share, sorry!

[CanuckQx4]

can you PLEASE post a picture of a harness that is capable of doing this to our cars.

Much appreciate

[Buzzman]

2nd that: More details on the harness, and what it's for, etc.
Thx.

[miamiheat3332]

wow i thought you had some serious wiring problems reading this, but to make it only one of those block connectors unplugged it surprising. Please do post this pic, as perhaps they may come loose for someone else and they will have same problem.

[wmcvetty]

I'll be sure to do that guys. Think it was D206 on the rear hatch harness in the FSM. More details to come.

[wmcvetty]

Just looking at the FSM, I confirmed it was D106 that connected to D206 that was unplugged. It is labled with an asteric that states not to unplug it unless following the Workflow or the ECM could throw codes (or something to that effect) and I was in fact throwing a Neutral Park Switch code that I purposefuly left that cleared itself today it seems.

I am wanting to dig some more, but it seems that everything that was used to create the overdrive issue was in this harness or the one beside it. Not sure how it is broken down between the two yet.

I have yet to see how any of this tied to the OD/Off issue though, but it may just be the nature of a missing ground that happened to show up in the OD circuitry?