starting problem

[icecreamman]

I took the Jeep to the dealership, I have the lifetime warranty and another one we got for almost nothing when I bought it. Figured let them give a look. It did it all last week but when I showed them it started fine. They had it overnight and it worked fine. They said they checked the nss and it wasn't that. One of their mechanics said he saw a couple Jeeps do the same thing and it's a connector between the ignition and the starter. He said they get water in the connector and shorts out. When they pulled the connector apart it was green and some water was still in it.
They replaced the connector and the starter under warranty. I dunno if that was the problem but I guess it's a good start and didn't cost me anything!

[cpak80]

Mines an 07 and does this any hot or humid day. I just turn key on and down to neutral then back to park in one movement and it starts every time

[Banned4life]

Should have read this thread first. Just replaced the starter and battery and checked every connection. Started fine got back home and won't start again. Now that I know this has anyone had any luck just replacing the numeral saftey switch?

[Vegasrobbi]

Should have read this thread first. Just replaced the starter and battery and checked every connection. Started fine got back home and won't start again. Now that I know this has anyone had any luck just replacing the numeral saftey switch?

My first post on Freaks

It's called a Transmission Range Sensor (TRS). It is mounted on the valve body and is a pain to replace. It has 4 small spring loaded contacts that slide on a plastic embedded metal plate as you move the shift lever.

It is a poor design from the 1980's, runs in hot and often dirty transmission fluid. We replace it with a Shift Lever Position (SLP) board of our own design. Starting in 2012 the JK went to a SLP module.

If the transmission is grounded well the TRS is simple to test. When it won't start ground the yellow/blue wire in connector 4 of your PCM, that will bypass the TRS. Be careful since it will start in any gear when grounded so be sure it is in park. Also be sure to unground before you shift from park or you will go into PRNDL error.

I install a TRS byass switch for my expedition customers so they don't get stranded. I had one guy from Canada use the bypass 16 times on his trek across the US.

[Vegasrobbi]

Should have read this thread first. Just replaced the starter and battery and checked every connection. Started fine got back home and won't start again. Now that I know this has anyone had any luck just replacing the numeral saftey switch?

My first post on Freaks

It's called a Transmission Range Sensor (TRS). It is mounted on the valve body and is a pain to replace. It has 4 small spring loaded contacts that slide on a plastic embedded metal plate as you move the shift lever.

It is a poor design from the 1980's, runs in hot and often dirty transmission fluid. We replace it with a Shift Lever Position (SLP) board of our own design. Starting in 2012 the JK went to a SLP module.

If the transmission is grounded well the TRS is simple to test. When it won't start ground the yellow/blue wire in connector 4 of your PCM, that will bypass the TRS. Be careful since it will start in any gear when grounded so be sure it is in park. Also be sure to unground before you shift from park or you will go into PRNDL error.

I install a TRS byass switch for my expedition customers so they don't get stranded. I had one guy from Canada use the bypass 16 times on his trek across the US.

[karls10jk]

Vegasrobbi- Can you tell us more about the product? It sounds like your company produces a piece that that is good for 07-11 JK's with auto trans. Where are the connections for the PCM??

Would you suggest the TRS be the first place people look when they have starting issues?? Any figures on how common (or a percentage) of failures you see that the TRS is the issue vs adding an extra ground cable to the alternator.

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[Vegasrobbi]

Adding a ground doesn't hurt. The TRS picks up it's ground through the transmission shift shaft which is grounded by the case. So essentially be sure the transmission/engine are well grounded. The JK's main ground cables are marginal to start with. Be sure the ground studs on both inner fender wells are tight, and make sure the three way ground strap which goes from the hood to the firewall to the engine is there and tight.

For 2007-8 JK's be sure the software is up to date. There is a TSB for ESD(electro static discharge) which results in a no crank condition.
Antitheft System - Engine No Crank/No Start Condition NUMBER: 08-007-08 REV. A

If the software is up to date and grounds are good and you experience a no crank condition using the key go to the starter relay in the TIPM. Jump terminals 30 and 87 (use a relay tester if your not familiar with relays)[be sure it is in park!]. If it cranks each and every time at the relay but not at the key it is likely not the starter motor, grounds, battery, alternator, etc. I can't tell you how many times customers comes in and say I have an intermittent no crank and they replaced the battery, starter and alternator. I have seen dealers upgrade grounds and replace parts and not fix the condition.

At this point go to connector 4 of your PCM, grab the yellow/blue wire. Go back and crank with the key and if it starts you most likely have a bad TRS. Sometimes adjusting the shifter cable helps; or, shift into neutral and try to start, or just jockey the shift handle around and if it starts it most likely is the TRS. The TRS plate gets grooves worn on the surface, the springs behind the pins are very weak, like a ball point pen springs. Combine this with dirty hot transmission fluid and a worn shift shaft and there just isn't enough ground available to send a signal to the PCM. Some may experience a momentary crank and shut off. Enough continuity is available to set the circuit off then once the circuit is under load the ground drops out and results in no crank, you get a click.

One solution is to get the TRS out of the transmission and put it in a less hostile environment. We add a linear pot to the shift lever which tells a digital circuit the shift lever position(SLP) to within a few thousandth's of an inch. Jeep started doing a similar set up starting in 12'. Our circuit is programmable so each position is memorized and the memory is non volatile; this way if the battery is disconnected the memory is saved. In addition it is designed to always ground the N/S wire when the lever is in Park or neutral so you don't get stuck, even if there is a PRNDL error.

The TRS has 6 wires going to it, two are for the transmission temperature sensor, the other four are the four pins on the TRS. Since the early Jk has a Powertrain Control Module the transmission functions are controlled by the NGC4 computer up by the windshield washer bottle. The automatic transmission functions are routed to connector 4 of the NGC4, the one closest to the engine, that is why there is no connector 4 present on manual JK's. The 4 PRNDL wires essentially feed the PCM a 7 segment driver signal which the PCM translates into shift lever position. It uses this information for neutral safety functions, reverse lights, the PRNDL on the dash(VFD) and of coarse engine performance.

We use our circuit primarily for V8 swaps; however, we have sold several to guys who don't want to mess with replacing the TRS.

[karls10jk]

That's good information to know and you certainly paint a vivid picture of the happenings within the transmission. Luckily I've got a manual so I can use this info to assist others.

So you've designed this piece, is it proprietary or did you adapt it from another application or just use the 12+ and retro fit it? Also- you mention the trans fix, taking in customers with no start conditions, and v8 swaps......what kind of shop is it that you've got? Furthermore.....did the SLP come out of necessity from a bad design from the factory or was it something you put together for your v8 swaps and just applied it to the stock application to correct an issue? (Albeit if you simply retro'd the 12+ unit then obviously it didn't come from v8 swaps and so forth)

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[Vegasrobbi]

That's good information to know and you certainly paint a vivid picture of the happenings within the transmission. Luckily I've got a manual so I can use this info to assist others.

So you've designed this piece, is it proprietary or did you adapt it from another application or just use the 12+ and retro fit it? Also- you mention the trans fix, taking in customers with no start conditions, and v8 swaps......what kind of shop is it that you've got? Furthermore.....did the SLP come out of necessity from a bad design from the factory or was it something you put together for your v8 swaps and just applied it to the stock application to correct an issue? (Albeit if you simply retro'd the 12+ unit then obviously it didn't come from v8 swaps and so forth)

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We put GM LS engines in Jk's. LSWrangler.com. MoTech is our company name. The LS is light, powerful and compact. An LS JK drives like no other JK, especially when combined with the 6l80 6 speed clutch to clutch automatic transmission. Our customers include John Currie, Phil Howell, EVO, Poison Spyder..... We don't advertise and word of mouth has kept us busy. You have a build thread on JKfreaks now at MoTech, a 430 HP all aluminum LS3 20110 JKR. Our SLP board was developed to allow full function of the Jk systems with an LS engine installed. It's different with a Hemi since it shares a common OS with the JK. Our swaps support virtually all JK systems with the LS engine installed, like it came from the factory that way. The SLP circuit is just part of what makes it all happen. It is a proprietary design, we work with an EE closely to develop these circuits. The circuits use microprocessors and are built to military standards, we have not had a failure yet.

The 2012's already have an SLP circuit installed so when we do a 12' swap we simply use it. The earlier JK's cannot use the 12' SLP since the OS's are very different. The 12' SLP is actually a module integrated into the bus so it is not easily fitted to any other application.

[karls10jk]

Yes.....I've checked out MoTech before and realllllllllllly like the LS swaps, but I could be partial since I've got some experience with the corvette's and the power they lay down.

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