Transmission problem apparently has nothing to do with transmission
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Transmission problem apparently has nothing to do with transmission
so I am having a problem with my Jeep where on startup it won't shift into 4th gear and once I restart the car it will but when in the 1/2 position won't shift into first(starts in 2nd) but above 30 will lock itself into first no matter the speed. These two problems happen but it appears not at the same time, only one is occurring at a time. This problem we had before and we tested TCM, replaced throttle position sensor, adjusted kickdown cable multiple times, replaced the entire transmission(with known good one) along with sensors/wiring from the car down(where it splits from the main wiring harness), and yet still the same problem we had before. I'm at a loss and want to know if anybody here has any clue about what sensors or other stuff could be causing the issue.
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1998 XJ
4.0 I6 engine
4wd NP231(also out of the 2000 cherokee)
Transmission is AW4 out of a 2000 Cherokee that did not have this problem
I'm honestly stumped because we were guessing that swapping the whole transfer case/transmission would fix the problem, but I guess not.
4.0 I6 engine
4wd NP231(also out of the 2000 cherokee)
Transmission is AW4 out of a 2000 Cherokee that did not have this problem
I'm honestly stumped because we were guessing that swapping the whole transfer case/transmission would fix the problem, but I guess not.
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Joined: Dec 2015
Posts: 935
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From: Nationwide, USA
Year: 89
Model: Cherokee
Engine: Renix 4.0
I’m no expert by any means, but it sounds like symptoms of bad shift solenoid(s), but as you said it seems highly unlikely to have the same problem with two transmissions. I know you said you tested the TCU, but is this part swappable from the other XJ?
Having ruled out nearly everything else, I’d have to suggest cleaning all the grounds you can find. May be a lame suggestion but it never hurts.
Hopefully someone with more knowledge than I will chime in…
Having ruled out nearly everything else, I’d have to suggest cleaning all the grounds you can find. May be a lame suggestion but it never hurts.
Hopefully someone with more knowledge than I will chime in…
Last edited by ElMartillo; Dec 26, 2025 at 06:36 AM.
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Joined: May 2013
Posts: 43
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From: Toledo, WA
Year: 1988
Model: Comanche (MJ)
Engine: 4.0
Anything in this writeup give you any ideas? Seems like it's misinterpreting the speed signal. You have OBDII so you might be able to get some clues from realtime data.
First step to any electrical issue is clean connectors and grounds.
First step to any electrical issue is clean connectors and grounds.
Thread Starter
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really unlikely to have the problem be the solenoids after it didn't have any miles driven after the swap for the issue to still be prevalent. I scrapped the other Jeep already and the TCU is swappable, but I swapped them to test and had the same symptoms. I'm probably about to have to do that, what sucks is this is the cleanest Jeep I've seen for it's age and I'll have to see but all the grounds look spotless from the one's I've seen while I've been digging, I'll have to try to find more though.
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Not at a first glance, I'll dig deeper though, I know when I checked last it has no OBDII Codes being thrown like at all with the Realtime data I checked looking good. Any realtime data I should be looking for specifically?
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Junior Member
Joined: May 2013
Posts: 43
Likes: 9
From: Toledo, WA
Year: 1988
Model: Comanche (MJ)
Engine: 4.0
Mostly just interested if your speed signal is getting read correctly at the ECU.
Did you check your grounds with a multimeter? A lot of our grounds are on paint and only actually ground in the threads, hard to tell visually. I use a multimeter on ohms with one lead clamped on the negative stud, then poke the ground wire at the devices with the other lead.
PowerProbe is my favorite tool for doing this, but multimeter works fine.
Did you check your grounds with a multimeter? A lot of our grounds are on paint and only actually ground in the threads, hard to tell visually. I use a multimeter on ohms with one lead clamped on the negative stud, then poke the ground wire at the devices with the other lead.
PowerProbe is my favorite tool for doing this, but multimeter works fine.
Senior Member
Joined: Dec 2015
Posts: 935
Likes: 49
From: Nationwide, USA
Year: 89
Model: Cherokee
Engine: Renix 4.0
really unlikely to have the problem be the solenoids after it didn't have any miles driven after the swap for the issue to still be prevalent. I scrapped the other Jeep already and the TCU is swappable, but I swapped them to test and had the same symptoms. I'm probably about to have to do that, what sucks is this is the cleanest Jeep I've seen for it's age and I'll have to see but all the grounds look spotless from the one's I've seen while I've been digging, I'll have to try to find more though.
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You said that you replaced the TPS, but did you also calibrate/adjust it?
Backprobe the connector with the Jeep on (not running), you HAVE to have it connected, because you need to check baseline sensor voltage against output voltage, and ohm the ground too.
It's also easy to manually trigger the solenoids (basically, you are the TCU) to test if that is the issue.
Also (this is true on my 1990 Renix, pretty sure it applies to the HO's) you can unplug the TCU pigtail completely, and then you should be able to manually shift with the PRNDL lever, so, this can help differentiate between an actual transmission problem, and an electronic one.
TPS TEST
You should have 5 volts going into the Throttle Position Sensor (TPS). It is best 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. At idle, TPS output voltage should be greater than .26 volts but less than .95 volts. Move the throttle and look for smooth meter response up to the 4.49 at WOT. The other wire will be the ground and should show no voltage.
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:
-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 faulty TPS can report values outside the 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 excessive misfires resulting in one or more cylinders being shut down to prevent engine and catalytic converter damage.
.
CPS Testing
.
TESTING PROCEDURE 1991 - 2001 4.0L H.O. engines
1. Near the rear of intake manifold, disconnect sensor pigtail harness connector from main wiring harness.
2. Place an ohmmeter across terminals B and C (SEE Image). Ohmmeter should be set to 1K-to-1OK scale for this test.
3. The meter reading should be open (infinite resistance). Replace sensor if a low resistance is indicated.
You should have 5 volts going into the Throttle Position Sensor (TPS). It is best 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. At idle, TPS output voltage should be greater than .26 volts but less than .95 volts. Move the throttle and look for smooth meter response up to the 4.49 at WOT. The other wire will be the ground and should show no voltage.
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:
-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 faulty TPS can report values outside the 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 excessive misfires resulting in one or more cylinders being shut down to prevent engine and catalytic converter damage.
.
CPS Testing
.
TESTING PROCEDURE 1991 - 2001 4.0L H.O. engines
1. Near the rear of intake manifold, disconnect sensor pigtail harness connector from main wiring harness.
2. Place an ohmmeter across terminals B and C (SEE Image). Ohmmeter should be set to 1K-to-1OK scale for this test.
3. The meter reading should be open (infinite resistance). Replace sensor if a low resistance is indicated.
It's also easy to manually trigger the solenoids (basically, you are the TCU) to test if that is the issue.
Also (this is true on my 1990 Renix, pretty sure it applies to the HO's) you can unplug the TCU pigtail completely, and then you should be able to manually shift with the PRNDL lever, so, this can help differentiate between an actual transmission problem, and an electronic one.
Last edited by Mittnz; Jan 3, 2026 at 01:43 AM.
Thread Starter
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I do know it isn't a actual transmission problem because we just swapped in this transmission that we know is good, I was unaware that the TPS as to be calibrated? I've calibrated the kickdown cable but didn't see anything about calibrating the TPS?
Thread Starter
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I'm hoping this isn't my issue, was your problem like what I've described at all? I don't think the PCM is the original and has been replaced already, last I pulled the codes I noticed that the vin doesn't match between the dash and what pcm pulls.
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It has p07c0 which I believe has to do with speed signal? I just pulled the codes and there was a pile that have showed up, but this is the only transmission code along with P0700 which from my previous research means something is wrong in Transmission, no real details but my guess is it's being caused by p07c0