My brother-in-law has a Ford/Mazda Explorer/Navajo.
I got a call today that the O/D light was flashing, and the car was shaking and had no power. When I got home from work, the car drove fine, except for one instance at a traffic light where it seems the transmission was stuck in
3rd, and the car shook and the engine stalled. No O/D light flashing.
I know that the flashing O/D light means the transmission control module is communicating a malfunction. My question is, is the malfunction stored as an OBD II Code that I can read in the same manner as reading codes from the Check Engine light?
Hmmm...since this is a Toyota group, and all I have are older Toyotas and a Mazda and a Subaru or two, the best I can come up with is, there is a test mode connector that flashes the O/D indicator like the old CHECK ENGINE lights on Toyotas. How you get to it in a Ford...?
Because the Toyota group 1.) is far more active than the Ford Group -- although most of the activity isn't auto-related -- and 2.) has lots of people that know what they are talking about.
Because Jeff is a long standing member in the Toy group, and there are some of us here that actually know there are other manufacturers besides Toyota!
I just pulled codes, and there aren't any. I was expecting a code in the P0700 range, but there's nothing at all. The O/D light is not flashing, but it was, and the Check light is not on and never has been.
Yeah, I thunk of that. It's the hard part though -- it's my siter in law's car, and getting her to do more than put gas in the tank is a daunting task, having her work the scanner in the midst of a malfunction is not in the cards.
The problem does not happen with enough regularity to catch it in the act. It happened to her once, and she was on her way to my house anyway, so she just parked the car. I drove about 10 miles without any trouble, then at the stop-light, it acted up once, but never again.
I was thinnking of a transmission problem -- controller module or something -- because it shook the car and stalled the engine in D, but not P, R, or N. I was experimenting with the different selections but the light changed to green and I had to move on. I selected 1, and it was okay, and as I got up to speed, I selected D again and never had anymore trouble. The O/D light did not flash for me, but my sister says it flashed for her. The Check Engine light did not come on for her or for me.
I was expecting a transmission failure over a torque converter because the TC should have been a problem in R, and 1. My sister said she started in 2, and it was okay, but not very strong -- which is expected, I think. I'm not alarmed at any lack of power in a 2nd gear start, but if the shaking stops in any selection other than D, that would seem to discount the TC in my mind.
My guess is that there is no problem in R or 1 because the TC does not lock in R or 1 but it does lock in D. The lack of power in 2 is because the TC was locked and there is no torque multiplication.
The TC is for all practical purposes, a centrifugal clutch, is it not? I get that it is far more complicated than that, but it's basic function is the same. Would the TC be locked in D while the car is not moving, but not be locked in 1 or 2 or R under the same conditions? I thought that the lockup did not come on until a certain speed condition was reached.
The transmission also has a lock that effectively drops the pump-action of the fluid and makes a direct drive connection with the engine.
As for the car having no power upon start up in 2, yes, the gear selection will cause the power curve to be very flat until 20-ish mph is reached.
The torque converter, or TC, is for all practical purposes a fluid coupling. Think of an impeller or fan on the engine side that spins fluid against a stator or stationary fan, which redirects the fluid against the vane, which turns because of the movement of the fluid against it. The vane is connected to the input shaft of the transmission. A side advantage of the TC setup is torque multiplication, which helps move the vane from a standstill. As the speed of the vane approaches the speed of the impeller, efficiency is lost so the impeller and vane are mechanically locked together when the TC lockup clutch receives a signal from the transmission ECU. In other words, although the TC is locked mechanically, it is controlled electronically and not through a centrifugal clutch.
I'm not sure what you mean by "pump-action of the fluid in the transmission, but the ATF does not provide any motive force. The movement of the ATF inside the transmission case applies pressure against clutch packs and brakes which work on the planetary and sun gears, but the fore that causes the transmission output shaft is all supplied by the input shaft, which is powered by the torque converter.
The transmission is electronically controlled, and TC lockup is controlled by a solenoid, which is basically an electromagnet.
There are several possible causes for the TC not unlocking when the vehicle comes to a stop.
I am not familiar with the vehicle in question, but if the parts of the circuit that tell the transmission ECU to unlock are malfunctioning, the ECU would not know to send the unlock signal to the TC lock. For example, in a Toyota, when the brakes are applied, voltage in the brake light circuit that is controlled by the brake light switch tells the ECU to unlock. If the circuit is damaged, the voltage might not get to the ECU, telling it to unlock.
It is possible that the TC lockup device or solenoid is sticking and not unlocking.
Some automatic transmissions downshift as vehicle speed drops and the throttle is closed, and some do not downshift until the throttle is opened, which spins the TC, which builds pressure in the transmission, which causes the downshift. If the vehicle comes to a stop and the downshift has not occurred yet and the TC has not unlocked, you will get the symptoms you described. If the driver shifts to low or R range, the TC lockup solenoid never gets a lockup signal, so it doesn't get stuck in the locked position.
I think the cause of the symptoms may be electrical - damaged wiring to the brake light circuit, lockup solenoid circuit, or speed sensor circuit, with the brake light circuit being most likely since a problem with that circuit wouldn't store a code.
Thanks, that helps me alot. You have provided me a few details that I did not know, but did know the general principles.
I _think_ (by the feeling in the seat of my pants) that the downshift does not always happen. It seems to happen right all of the time, except the time it didn't for my sister-in-law, and the time it didn't happen for me.
I'm thinking of a mechanical error over an electrical one, but again I'm driven by the seat of my pants. My instinct is that the lockup selonoid is getting the signal to unlock, but is sticking. It seems to me that if an electrical issue was at play, it would be happening with greater consistancy.
My brother in law is taking the car to have the transmission flushed and filter changed and so on. I'm not sure what sort of service the transmission needs in the way of filter changes and such, but he's gonna do that before he starts looking for parts failures.
If the control unit was looking for the brake signal to make a decision, would it be safe to assume that if the transmission was having a failure because the brake signal was missing, then the brake lights might be missing too? I once had a Chevy that would go to full throttle after releasing the brake pedal. It was spooky to say the least. If the Cruise was on, and the brakes applied, the cruise would cut out while slowing, but then Resume would kick in as soon as the brakes were released and full throttle would be engaged, usually in an instance when it was VERY undesirable. I once had this happen on an offramp, and the guy behind pulled up at the light and told me that the brake lights did not work. It was a warranty issue, so I took it in.
If the vehicle has more than 80k miles and has never been flushed before, I wouldn't start now. Just drain nand refill..
I don't know the setup on the vehicle in question and there is more than one way to accomplish the task. One way is to have the ECU on a parallel circuit with the lighting wiring; another is to have another switch mounted next to the brake light switch that serves the ECU and cruise control. If there is a loose connection or pinched wire in the parallel circuit or extra switch circuit, the problem would probably be intermittent.
On Fri, 11 Sep 2009 11:14:01 -0700, Jeff Strickland rearranged some electrons to say:
Not at all. It is a fluid coupling that is also a torque multiplier. It also has a lockup clutch that is electrically controlled that locks the turbine and the stator together to improve the gas mileage.
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