Gillette1987

I know I'm bringing up an issue everyone else has on the tranny issues here, so bear with me.

I've read up on everything and wanted to start fresh on MY rig... Transmission fluid and filter was changed out, is clean and clear as it should be. It doesn't shift from 1st to 2nd without me letting up on the gas and back down again. Read that it could either be the TPS or TPC (what does TPC stand for???)

I unplugged the main harness from the box under the passenger "knee board" and manually shifted from 1, 2, 3, to D and had no slipping whatsoever so I know it's not the TPS or internal tranny. Hoping to swap out the electrical box under the passenger knee board this weekend to see if this resolves the tranny shifting issue.

Lemme know if I'm missing anything?

JeepMN

Having the exact same issue as you. I've been told to clean out the NSS but I don't think they are related issues.

Are you getting a CEL?

jakbob

You have that backwards. By unplugging the TCM and shifting manually, all you are doing is using the internal hydraulics of the trans to shift.

Sounds like the TPS is the issue. Search for cruiser54's renix procedures and start there.

jakbob

And also, when you are trying to shift from 1-2, what gear selection are you in?

tjwalker

I agree. If it shifts fine manually without the electronics involved, then this is an electronics issue.

Start with testing the throttle position sensor. Pretty common failure on the 4.0
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RENIX TPS ADJUSTMENT

Before attempting to adjust your TPS be sure the throttle body has been recently cleaned. It's especially important that the edges of the throttle butterfly are free of any carbon build-up.

IMPORTANT NOTE: With the Key OFF, and using the positive (red) lead of your ohmmeter, probe the B terminal of the flat 3 wire connector of the TPS. The letters are embossed on the connector itself. Touch the black lead of your meter to the negative battery post. Wiggle the wiring harness where it parallels the valve cover and also over near the MAP sensor on the firewall. If you see more than 1 ohm of resistance, or fluctuation in your ohms reading, some modifications to the sensor ground harness will be necessary. The harness repair must be performed before proceeding. I can provide an instruction sheet for that if needed.

MANUAL TRANSMISSION:
RENIX manual transmission equipped XJs have only a flat three-wire TPS mounted on the throttle bodyand it provides data input to the ECU. It has three wires in the connector and they're clearly embossed with the letters A, B, and C. Wire "A" is positive. Wire "B" is ground. Key ON, measure voltage from "A" positive to "B" ground by back-probing the connectors. Note the voltage reading--this is your REFERENCE voltage. Key ON, back-probe the connector at wires "B" and "C". Measure the voltage. This is your OUTPUT voltage. Your OUTPUT voltage needs to be seventeen percent of your REFERENCE voltage. For example: 4.82 volts X .17=.82 volts. Loosen both T-20 Torx screws attaching the TPS to the throttle body and rotate the TPS until you
have achieved your desired output voltage. Tighten the screws carefully while watching to see that your output voltage remains where it is supposed to be. If you can't achieve the correct output voltage, replace the TPS and start over.

Sometimes, after adjusting your TPS the way outlined above, you may experience a high idle upon starting. If that happens, shut the engine off and reconnect your probes to B and C. Start the engine and while watching your meter, turn the TPS clockwise until the idle drops to normal and then rotate it back counterclockwise to your desired output voltage.

AUTOMATIC TRANSMISSION: RENIX automatic transmission equipped XJs have a TPS with two connectors. There is a flat three-wire connector, same as the manual transmission vehicles have, and it is tested the same as the manual transmission equipped vehicles, as outlined above—FOR ALL ENGINE MANAGEMENT RELATED ISSUES.

However, the automatic TPS also has a square four-wire connector, clearly embossed with the letters A,B,C, and D. It only uses three wires and provides information to the Transmission Control Module. THIS SQUARE FOUR WIRE CONNECTOR IS USED FOR TRANSMISSION/SHIFTING RELATED ISSUES ONLY. Key ON, measure voltage between "A" positive and "D" ground. Note the voltage. This is your REFERENCE voltage. Back-probe the connector at wires "B" and "D". Measure the voltage. This is your OUTPUT voltage. Your OUTPUT voltage needs to be eighty-three percent of your REFERENCE voltage. For example 4.8 volts X .83=3.98 volts. Adjust the TPS until you have achieved this percentage. If you can't, replace the TPS and start over. So, if you have an automatic equipped XJ your TPS has two sides--one side feeds the ECU, and the other side feeds the TCU.
FOR AUTOMATIC TRANSMISSION RELATED ISSUES: Check the square four-wire connector side of the TPS.
If you have ENGINE ISSUES check the flat three-wire connector side of the TPS.

For those with a MANUAL TRANSMISSION--the TPS for the manual transmission XJs is stupid expensive. You can substitute the automatic transmission TPS which is reasonably priced.

Danielxj

Having some what of the same issue. Tranny won't shift
From 2nd to 3rd or OD. and when it wines out in second instead of shifting into third it goes to neutral and the engine revs up. I'm going to try and unplug the TCM and check the tps also. Thanks for the write up.

Danielxj

Hey just a thought , to test the tps can you just unplug it at the throttle body and see if the tranny still behaves the same ?