landtortise

So i have a 95 xj 5.5 la 33's. Ect anyway. So i was driving thru the desert the other day when it was hot when I got back on the highway my tranny wouldnt shift automatically. Limped it home let it cool down got in it and it worked fine again. so i drove it for a.couple days and the. It quit shifting again. The fluid was dirty so i did a filter fluid change on it and it still wont shift automatically. Have all the gears manually. What could it be tcm? Governor soleniod? I need it to work. So please help.

BuckB91XJ

If when it quits shifting automatically, it will always still shift manually like you say. That is the TCU shutting off. My guess is since you get it back after letting the Jeep sit, it must be slowly going bad and it shuts off when it gets warm.

landtortise

ok so where to get one? that was kinda my thought the po said it did this to him and wouldn't is what he told me when I got it but we swapped the batteries when I got it and then it worked fine so I thought he was Full of S*** but now it won't work at all.

landtortise

just read another post about an 89 having the same issue and he was talking about a inline fuse for the tcu and it had blown and caused the same issue. does a 95 have the same fuse set up?

landtortise

well it manually shifts into 1st skips 2nd hits 3rd and I OD but the torque converter doesn't seem to be going into lockup.

BuckB91XJ

Yep, that starting in 1 and skipping 2 is because without the TCU you have no 1-2 shift. You only get the gears on the selector...1, 3, D. That is a limp mode the tranny goes into when the TCU loses power, so you can still drive it good enough to get home or to a shop.

BuckB91XJ

I actually have a manual switch hooked up to my TCU, to turn it on and off, so when I am trail crawling I can get my Tranny to stay in 1st gear without doing the auto shift into 2nd while I'm 4wheeling.

jebmccall

that wont tear up the trans?

but yes that is the tcu losing power/ not communicating. i have to make mine a "manual" to make it pass emissions.

BuckB91XJ

nope, all it does is turn the TCU on and off.

tjwalker

The TCU is certainly a possibility, but before condemning the TCU, I would be sure that you verify the "throttle position sensor".

Input from that sensor is directly involved in shifting characteristics of the AW4 transmission. And it fails more often than the TCU.

Here is how to test it. Good luck!
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The throttle position sensor is connected to the throttle shaft on the throttle body. It sends throttle valve angle information to the PCM. The PCM uses this information to determine how much fuel the engine needs. The TPS is really just a simple potentiometer with one end connected to 5 volts from the PCM and the other to ground. A third wire is connected to the PCM. As you move the accelerator pedal with your foot, the output of the TPS changes. At a closed throttle position, the output of the TPS is low, about a half a volt. As the throttle valve opens, the output increases so that, at wide open throttle, the output voltage should be above 3.9 volts. Testing can be performed with an electrical meter. Analog meter is best. You are looking for a smooth sweep of voltage throughout the entire throttle band. While slowly opening and closing the throttle, take note to the movement of the voltmeter needle. There should be a direct relationship between the needle motion to the motion of the throttle. If at anytime the needle moves abruptly or inconsistently with the movement of the throttle, the TPS is bad

You should have 5 volts going into the TPS. At idle, TPS output voltage must be greater than 200 millivolts. At wide open throttle (WOT), TPS output voltage must be less than 4.8 volts.. The best is to use an analog meter (not digital) to see if the transition from idle to WOT is smooth with no dead spots. With your meter set for volts, put the black probe on a good ground like your negative battery terminal. With the key on, engine not running, test with the red probe of your meter (install a paper clip into the back of the plug of the TPS) to see which wire has the 5 volts. One of the other wires should show .26V (or so). The other wire will be the ground and should show no voltage. Move the throttle and look for smooth meter response up to the 4.49 at WOT.

Perform the test procedure again and wiggle and/or tap on the TPS while you watch the meter. If you notice any flat spots or abrupt changes in the meter readings, replace the TPS.

The TPS is sensitive to heat, moisture and vibration leading to the failure of some units. The sensor is a sealed unit and cannot be repaired only replaced. A TPS may fail gradually leading to a number of symptoms which can include one or more of the following: -

NOTE: The throttle position sensor is also DIRECTLY involved with transmission shifting characteristics! It should be verified early in the troubleshooting process, when a transmission issue is suspected!

• Poor idle control: The TPS is used by the ECU to determine if the throttle is closed and the car should be using the Idle Air Control Valve exclusively for idle control. A fault TPS sensor can confuse the ECU causing the idle to be erratic or "hunting".
• High Idle Speed: The TPS may report faulty values causing the engine idle speed to be increased above normal. This is normally found in conjunction with a slow engine return to idle speed symptom.
• Slow engine return to idle: A failing TPS can report the minimum throttle position values incorrectly which can stop the engine entering idle mode when the throttle is closed. Normally when the throttle is closed the engine fuel injectors will be deactivated until a defined engine RPM speed is reached and the engine brought smoothly to idle speed. When failing a TPS will not report the throttle closed and fueling will continue causing the engine to return to idle very slowly.
• Engine Hesitation on Throttle Application: The TPS is also used by the ECU to determine if the driver has applied the throttle quicker than the Manifold Air Pressure sensor can read. The fueling is adjusted accordingly to cope with the sudden increase in air volume, however a faulty sensor can cause the ECU to ignore this data and the engine will "hesitate" when applying the throttle. In extreme cases with the engine at idle, a sudden application of full throttle can stall the engine.
• Engine Misfire: A fault TPS can report values outside the denied acceptable range causing the ECU to incorrectly fuel the engine. This is noticeable as a slight misfire and can trigger the misfire detection software and/or Malfunction Indicator Lamp (MIL) light on the dashboard. Extreme cases can cause excessing misfires resulting in one or more cylinders being shut down to prevent engine and catalytic converter damage.

landtortise

Tj thanks for the info I am headed out right now to test the TPS even tho I jut recently replaced it.

landtortise

alright I tested my tps. one wire has 4.93-4.97 volts the other reads around .70-.88 volts when i take it up to WOT i get 3.79-3.85 is this a bad TPS?

dan8yourv8

my trans was acting like that when i put my hood vents on and the tps got wet and shorted out

landtortise

I did drive thru a big puddle/creek crossing when I was out in the desert. But I didn't splash thru it too hard and I swapped the old tps back in and got the same results.

BuckB91XJ

So you did buy a new TPS when you didn't know for sure it was good or bad. I'm pretty sure that whole long write up by tjwalker was to help prevent you from throwing parts at your Jeep aimlessly. My TCU diagnosis wasn't just opinion. I create this "problem" you say you have every time I flip the inline toggle switch I installed in my TCO power wire to turn my TCU's input power off so I can lock my tranny in 1st gear for trail crawling. So, I know exactly the problem you are having and I told you what you need to do to fix.