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AW4 problem -TPS or speed control unit

B

Bill90XJ

Guest
The tranny (AW4) in my XJ will not shift out of first. It's not a mechanical problem but rather a electronic problem.

opps, 1990 I-6 Command-Trac

How do I determine if it is the TPS rather than the Speed sensor or vice-versa. Is there a test I can run with a multi-meter or any other test that will identify what the source of the problem is?

Thanks, Bill90XJ
 
My vote is your TPS,your on the right track.Thats exactly what happened when mine went out completely.First I had to run about 3000 rpm to get it to shift out of first then it wouldnt shift at all.Thats why I only paid $500 for my 90'.

Go to this site,and get the right way to check and calibrate your TPS.(http://members.tripod.com/BillyXJ/SENSORS1/index.html).Sorry dont know how to make a direct link.It helps to just print it out to refer to when testing.
GOOD LUCK
 
RINGKONG said:
Make sure your TCU is plugged in or good...

Ringkong - how do I make sure the TCU is good.

That's the question I asked.;)

TIA, BIll90XJ
 
First step (always) for the TCU tests is to mate/de-mate the connectors -- all of em -- start at the TCU and work your way out - include the Square TPS connector and the tranny harness... and to check the in-line fuse (if my memory is right it's in a Yellow wire near the TCU, but it's been a LONG time!)

The FSM describes a few tests (I don't have the AW4 FSM in-hand though - sorry).

If you're really in 1st gear than the fuse is good (CHECK ANYWAY!) -- the "no power" condition for the AW4 is 4th gear with the Torque Converter unlocked -- it'll get you where you're going, but damn does it get hot!

If you've checked the TPS (or swapped it) and disconnected and reconnected all of the TCU related connectors, you may wanna watch the voltage on the TCU's connector (socket c15 -- should be Violet with a trace-stripe) - this is Solenoid #2... If you're really in 1st gear Solenoid #1 is already engaged (socket c16 which is Blue with a tracer) , and Solenoid #2 needs to pull in to get you to 2nd gear (Sol-1 will stay on in 2nd and then shut off in 3rd & 4th)...

The Tranny connector has Sol-1 at at socket "G" and Sol-2 at socket "F" --

I know it's not much, but hopefully it'll BTT/Bounce this so you can get it resolved.
 
TPS-adjust

TPS - 1987-1990

The 1987-90 sensor has two pigtail leads. One has an in-line 3 pin
connector, containing 3 wires. The other has a square four pin
connector with 3 wires. The square connector is the one that is used
for the transmission controller. These wires can be identified by the
letters which are stamped into the connector.

Adjustment is simple though backward by most TP standards. With the
harness connected, test the voltage on pins A, B & D. The voltage on
pin A (reference voltage) should be approx. 5v

Voltage on pin D (ground) should be less than 0.1v. If the voltage is
higher, an additional ground wire can be spliced into the circuit.

Pin B is the TPS signal to the controller. The voltage on pin B should
be 4.0 - 4.4v at closed throttle. At full throttle, the voltage should
be 0.2-0.5v. The TP sensor has elongated holes for the hold-down screws which allow it to be ajusted.

Adjustment is as follows: (comments in brackets are mine)

1. Turn the ignition switch to the "ON" position

2. There are 2 wire harness connectors attached to the TPS. Inout/output voltage is checked at the SQUARE, FOUR TERMINAL CONNECTOR (though it only actually has 3 pins). The terminals are identified by the letters A,B,C,D molded into the connector.

3. Do not unplug the connector. The voltmeter leads must be inserted through the back of the connector to make contact with the terminals. Connect the positive lead to terminal A and the negative lead to terminal D.

4. With the throttle plate in the closed position, note the "input" voltage. It should be approx 5.0 volts

5) Remove the voltmeter positive lead from terminal A and connect it to terminal B. The "output" voltage should be 4.2 volts - 82% of input voltage. (NOTE: on my XJ, the input voltage was only 4.6 volts so I had to adjust the closed throttle output voltage to 3.8 volts as this is 82% of 4.6)
If this is not the case, continue with this procedure

6. Adjust output voltage as follows: with the voltmeter leads still attached to, carefully loosen the sensor mounting screws and slowly rotate the sensor until the output reading is 4.2 volts with the throttle closed (or 82% of your input voltage). Then, toghten the sensor mounting screws securely.

=============================================================================

OK. Here's the deal with adjusting the TPS from the FSM. Using a DC voltmeter, check the voltage across the TPS' Gray and Black wires. Do this with the ignition on and at the TPS quick connector (C220) or at the C101 connector. The voltage should be 5.0V. Then check voltage across the TPS' black and blue wires with the ignition on and the throttle in idle position. The voltage should be 4.2V. If not loosen the TPS attaching screws and rotate the sensor until you have the 4.2V. Tighten screws and recheck voltage. These procedures are for the '88 4.0 L with auto. Someone on here said that Jeep put out a service bulletin that changed the setting from 15% to 20%. The 4.2V is 15% less than 5.0V, so 4.0V would be 20% less. Can anyone else confirm 15 or 20?
 
I got it!

Connector B that talks to the TCU was reading .1 volts. I swapped in another TPS that tested OK and road tested the rig. The tranny shifted as it should.

Thanks for your responses.

Bill90XJ
 
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