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Discussion Starter #1
First, it's an XL7 2004 model.

Got this from a dealer, BAD idea... it's needed thousands in new parts. Finally got it to a point I thought I'd have a good car for at least a few more years but no.

Transmission started slipping. OMG NO! Called my mechanic, said bring it in the morning, didn't get a half mile from the house when the car seems to forget it's in drive and locks up. He came and towed it in.

Now the nightmare.
The actual transmission is FINE. This is something electrical. His computer came up with some little plastic plug thing on the underside of the car. He showed me and yea, it's cruddy. Few hundred bucks worth of cruddy little plug but what ever, lets fix this.
Well it's still doing it. He thought perhaps something related to the brakes, which actually need work, calipers pulling. Not sure if there is a sensor in there too or not.
He tried calling Pro Transmission who won't even touch this thing.
So he has tried to research this but no luck.
Then he told me.... "you know why your clock doesn't work? It's because your airbag light is on. That's how wanky the system is in this car. Without an electrical schematic he can't track down where this problem is. And good luck FINDING such a schematic."
I located the only suzuki dealer left in the state of Michigan and THEY can't get a schematic.

My mechanic did replace that one bad plug, said he got it working but cannot guarantee it, and has already spent way too long on this one problem, he's tossing in the towel.

OH... before this happened, same mechanic has already replaced the motor, the alternator, starter, and belt. But with this issue, informed me he thinks at some point this car may have been underwater.
I asked why he couldn't figure that out while replacing the motor, and he said he wasn't looking for that.
Ok, I can see that since the plug is UNDER the car, maybe looking there wasn't part of it and I have no clue where assorted computers are in this car. So ok, that's possible.

Since I got it back, it only did this once. The drive light goes out, check engine comes on, and the car seems to forget if it's in drive, park, reverse, or what. BUT the mechanic told me if I lightly feather the brake, it puts it into "limp mode" and this does work. Cars drive light went back on and it worked again. This might be weather related and in fact the day it happened again it was raining. I've taken it out several times since and it's been fine. Even the check engine light went out on it's own. And it even worked on another rainy day.
Still I'm too afraid to put it on the highway. And even going into any town it's kinda nerve racking knowing at any time the car might forget it's in drive.
I can't stare at the dash board watching for a check engine or drive light all the time. With snow and ice season now, this is not at all good. I'm more or less stranded.


So... has anyone had this issue and solved it?
OR
Can anyone point me to where I might find a good electrical schematic for this particular model?

One last point, his assistant had trouble getting their reader to work, entering 2002 instead of 2004 seemed to help. But clearly there is still an issue.
 

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The first thing I'm going to tell you is if the transmission is slipping, the problem does NOT lie with the electronics, it's internal to the transmission. I also seriously doubt that the electronics are responsible for the transmission "forgetting it's in drive" - all the electronics do is select which forward gear you're in if D has been selected - Park/Reverse/Neutral/Drive are mechanically selected via the shift lever & cable, and you should be able to unplug the transmission and manually select gears with the shift lever.

The computers are in the dash - one, the ECU should be under the glovebox, the TCU should be left of the steering wheel, and BCM (Body Control Module) should be right side of the glovebox, near the top of the dash.

Unfortunately I can't assist with a schematic, what I have access to stops at the 2003 model year and there were significant differences with the 2004 refresh.
 

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Discussion Starter #4
The first thing I'm going to tell you is if the transmission is slipping, the problem does NOT lie with the electronics, it's internal to the transmission. I also seriously doubt that the electronics are responsible for the transmission "forgetting it's in drive" - all the electronics do is select which forward gear you're in if D has been selected - Park/Reverse/Neutral/Drive are mechanically selected via the shift lever & cable, and you should be able to unplug the transmission and manually select gears with the shift lever.

The computers are in the dash - one, the ECU should be under the glovebox, the TCU should be left of the steering wheel, and BCM (Body Control Module) should be right side of the glovebox, near the top of the dash.

Unfortunately I can't assist with a schematic, what I have access to stops at the 2003 model year and there were significant differences with the 2004 refresh.
" the problem does NOT lie with the electronics, it's internal to the transmission."

Wouldn't that be something my mechanic would know?
Why would this car's D light just go out, then it either locks up or randomly changes gears.. (done that too.) Tapping the brake resets it and the D light comes back on.
He is sure there is some computer glitch, or circuit or something but doesn't want to keep throwing multi hundred dollar parts at it. And I'd agree with that since I'm paying.
 

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slipping is internal to the trans, weird gear selection and changes are electronic. As Fordem has said, mechanically selecting D R Or N will make the car move (or not in N obviously). Shift points are then controlled by line pressures or the TCM . Unplug the trans and see if it slips.

Do the basics, check, clean and test all grounds and power supplies, the symptoms you describe are all attributable to bad connections. The fact you tap the brake and the indicator lights pop back up suggests a broken ground or power supply between the body and the engine/transmission. Check ALL the grounding points, make sure lugs and metal are clean and bright and no signs of corrosion on leads where the lugs attach.
 

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" the problem does NOT lie with the electronics, it's internal to the transmission."

Wouldn't that be something my mechanic would know?
I'm making no comment other than saying some wouldn't as they are code reading parts changers and not skilled in diagnostics or how things actually work.
 

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" the problem does NOT lie with the electronics, it's internal to the transmission."

Wouldn't that be something my mechanic would know?
Why would this car's D light just go out, then it either locks up or randomly changes gears.. (done that too.) Tapping the brake resets it and the D light comes back on.
He is sure there is some computer glitch, or circuit or something but doesn't want to keep throwing multi hundred dollar parts at it. And I'd agree with that since I'm paying.
Let me ask you this question ...

How should I know, what your mechanic, whom I don't know, should know???

The average mechanic is not a transmission specialist and many of them are hopelessly lost when it comes to the plethora of electronics in a modern vehicle.

If the transmission is slipping, the possible problem areas are worn clutch packs, low hydraulic pressure or a sludged up valve body preventing the line pressure from properly activating the clutch packs, random shifts between the forward gears can be caused by a defective transmission control unit, or by defective connections between the control unit and the solenoids that actually shift the transmission.

The transmissions of that era (including the one used on the XL-7 to 2003 drive the indicator lights from a physical switch on the end of the selector cable - no electronics involved - I suspect yours does the same.

Like 2013GV I suspect you have a grounding issue - try adding a heavy ground wire between the transmission housing, the vehicle frame and the battery negative - there should be one already, nut many mechanics forget to reconnect it after engine removal.
 

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Discussion Starter #10
First let me thank you folks for the help. I see a lot of stuff in here I need to ask about. Please know I am NOT a mechanic. I have a lousy 4 stroke motor on my bicycle I can't get going. No way I'd deal with a car. Not my thing. But I'm not a doctor either yet I still know how the heart works, basically. Same here. It's good to learn but someone else has to do this for me. I need to know what to clue them in to look for. Or ask if there is something they didn't check, such as a ground wire.
So please be patient with me. This is all very helpful.


The average mechanic is not a transmission specialist and many of them are hopelessly lost when it comes to the plethora of electronics in a modern vehicle.
YES!!!! SO TRUE. So first this information is something I will share with my mechanic and go from there, but... I have to wonder when he said he called Pro Transmission why they didn't want to deal with anything if it was electrical.
Perhaps I should just go there myself.

As for the actual transmission, I've been through enough cars to know what a bad trans feels like. They don't slip one time and not for weeks. When they go, they start to go and get worse till they don't go anymore. Right?
When this car is not having a brain fart, it's got plenty of pick up and go. NO slippage what so ever. Unless that drive light goes out, and suddenly who knows what will happen. Bad ground wire? I hope so cause that seems like an easy fix. Will definitely bring this up with him.

Thing is, right now it hasn't been doing it. Hard for any mechanic to troubleshoot something when it's working fine.


OH one last thing... just looked up limp mode. not much help, here.
What causes limp mode?
Here is a list of different possible causes of limp-mode.
  • Engine boost control, Overboost/Underboost.
  • Faulty engine sensors.
  • Faulty engine components.
  • Engine wiring issues.
  • Transmission issues.
  • Transmission wiring issues.
  • Brake system wiring issues.
So basically, SOMETHING is broken. But I would think since transmission is one of those things, a transmission specialist would know how to narrow this down?
 

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I don't know enough about auto transmissions to give any useful advice. I do however have wiring diagrams for the 2003 onward Grand Vitaras and XL7's. The ones with the updated dashboard which incorporates a "Body control module". Needless to say I can't guarantee this is correct for USA models. Relevant pages joined together......

95104
 

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Just to make things more difficult I have a 2003 print wiring manual just for the XL7 and it differs from above. It does show from these VIN numbers onwards

95105
 

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OH WOW! I will have to get out there and see if I can find that VIN number. WHY would they put that in a filthy dirty wheel well???? I'll look.
 

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Apparently 2004 is when a 5 speed auto was introduced. I have the relevant workshop manual and wiring diagram if this is the case. If the transmission was to be stripped down I also have the transmission workshop manual.
 

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On a US vehicle the VIN is visible through the windscreen to anyone standing near the driver's side.
 

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As for the actual transmission, I've been through enough cars to know what a bad trans feels like. They don't slip one time and not for weeks. When they go, they start to go and get worse till they don't go anymore. Right?
When this car is not having a brain fart, it's got plenty of pick up and go. NO slippage what so ever. Unless that drive light goes out, and suddenly who knows what will happen. Bad ground wire? I hope so cause that seems like an easy fix. Will definitely bring this up with him.

Thing is, right now it hasn't been doing it. Hard for any mechanic to troubleshoot something when it's working fine.


So basically, SOMETHING is broken. But I would think since transmission is one of those things, a transmission specialist would know how to narrow this down?
Transmissions can slip and then "come right" if they are having pressure control issues or have a sludge build up.
I have had a TH350 start to slip once in my ute when warm, then not do it for weeks until it failed on the open road. Clutch pack was all steels, no material left. The first single slip i felt was all the warning I had.

They don't always fail like you think they will.

The slip copuld be the pressure control solenoid having a fart, but I don't have the control diagrams for that trans handy to check what would happen if it suddenly stopped working, or whether it actually has electronic pressure control fitted.

As a test, run a heavy lead from a suitable bolt on the engine to the battery negative terminal and one to the body as well and see if any problems start to resolve themselves. You can do this yourself to save money.
 

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Thanks Darrell, hard to tell but I think it will have a pressure control solenoid. If that losing power then a slip momentarily could result.

G55 and G57, those ground points would be my first places to check onto the body, along with the E42 power supply line. It only takes a bit of crud on the fuse to cause an issue. Pull the IGN / Coil fuse and check it for any signs of corrosion on the fuse blades, and for a solid battery volts on the live side.
 
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