I have no overdrive or tcc lockup - 94 46RH

[Nealuss]

So recently I attempted to install a jet chip. I waited for a long while before pulling the trigger but I realized it was my only option for "tuning" so I went for it. Big mistake! After installing it, the PCM fuse blew causing the truck not to start. I found no bent pins, corrosion, etc. I tried to remove it but it fit so tightly to the harness connector that I had to destroy the chip to get it out. Finally got it out, found the blown fuse, and truck starts and runs now. I didn't have any fuses at the time so I pulled the one for the key/door buzzer. I very quickly noticed I had no O/D. I did a little reading and found out that fuse also powers the O/D switch. Put a new fuse in there and the truck still won't go into O/D. I have checked all of the pins on the PCM, I have power at the O/D, TCC, and trans control wires from the connector at the PCM, and the O/D switch lights up as it should meaning it is getting the signal from the PCM to do it's thing. I even cleaned out the female pins and tightened them all up to make sure they would make good contact. Before the whole Jet Chip debacle everything worked properly.

Sorry for the long read but I have spent a lot of time working this out so far and my eyes are bleeding from looking at wiring diagrams. Can anyone help?!?!

 

[Nealuss]

Anyone have any insight into this? Is there any specific circuit I should check that could cause this issue? Is it possible the PCM itself could be at fault?

 

[Travelin Ram]

Since you have all the wiring diagrams, I’d start by connecting a test light or meter to the TCC control wire close to the trans. With long leads and placed where you can see it and drive. Take a drive and see if the TCC receives a command to lock or not. Then you’ll know whether to investigate downstream into the trans or upstream into the PCM or sensors.

Have you tried disconnecting the battery for a while to reset the PCM?

Do you have access to the factory service manual troubleshooting flowchart? That should list all the potential causes for a condition and how to test. If not a subscription to something like Alldata or Tech Authority could give you that.

 

[Nealuss]

I have checked for signal from the pcm for the switch, trans control, tcc lockup, and o/d wires before and after the bulkhead connector. I have also checked all chassis grounds and 12v inputs at the pcm as well as pcm ground inputs. I also checked signal for the tps, iac, ect, vss and all are getting good signal (no surprise there since every sensor on the engine is new.) I did find the service manual online but it wasn't a ton of help. The flow chart didn't tell me anything I didn't already know. I haven't tried bypassing the pcm to engage the solenoids manually; that's my next step. I'm starting to lean toward the pcm itself. This all started because something backfed through the pcm when i tried to install the jet chip. 26 year old wiring and computer and power feeds through and blows a fuse...it sounds obvious when I think about it that way, but I don't want to throw money at a problem without properly diagnosing it.

 

[Dan98]

So recently I attempted to install a jet chip. I waited for a long while before pulling the trigger but I realized it was my only option for "tuning" so I went for it. Big mistake! After installing it, the PCM fuse blew causing the truck not to start. I found no bent pins, corrosion, etc. I tried to remove it but it fit so tightly to the harness connector that I had to destroy the chip to get it out. Finally got it out, found the blown fuse, and truck starts and runs now. I didn't have any fuses at the time so I pulled the one for the key/door buzzer. I very quickly noticed I had no O/D. I did a little reading and found out that fuse also powers the O/D switch. Put a new fuse in there and the truck still won't go into O/D. I have checked all of the pins on the PCM, I have power at the O/D, TCC, and trans control wires from the connector at the PCM, and the O/D switch lights up as it should meaning it is getting the signal from the PCM to do it's thing. I even cleaned out the female pins and tightened them all up to make sure they would make good contact. Before the whole Jet Chip debacle everything worked properly.

Sorry for the long read but I have spent a lot of time working this out so far and my eyes are bleeding from looking at wiring diagrams. Can anyone help?!?!

If you melted the jet cartridge into the plug you probably burned something in computer. I can send a pdf file showing witch wires go to lockup and od at trans plug and computer ends they short to ground when activated so I'm thinking if you have a open circuit in those 2 wires than there is a open or break somewhere. Low voltage with key on is normal ground when in overdrive open for problem.

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[ViolentMouse]

PCM pin #10 Red with white stripe. When you press the overdrive on/off button, this should change state. This is the signal to the ECM that overdrive is enable or not.
PCM pin #54 Red with a black stripe. This is the Overdrive off indicator. when you press the button, if the ECM is getting the proper signal to pin #10 this should change state.

If you have already checked that and you are getting signal to pin 10 and pin 54 is not changing state, then you likely cooked your ECM.

The next best move would be to grab a wiring harness and ECM from a 1996/1997 and convert to OBD2. This will allow for you to get a proper tuner on it and avoid JET products altogether.

Expect the obd2 ECM to have a death flash on it and allow enough finances to either buy an HP tuners interface and licenses... or reach out to hughes engines and get an SCT with some canned tunes. The preferred method here is the HP tuners dongle, but the SCT with canned tunes is an affordable start and there are at least two people still cooking tunes for it so you can datalog your vehicle, and have them send a custom tune.

Back in the days we used to use those JET inline chips and we put them on the dyno and found that eventually the computers closed loop adaptives would overcome any and all signal intercepts. The only way to properly "chip" an ECM is to have some old hardware that actually burned the ROM chips and you would go through no less than 20 chips to get a good tune.

This required soldering a chip socket into the ECM and cutting a hole in the cover so you could easily remove and replace ROM chips inside the ECM itself.

Sorry about your misfortune, hope you find a solid solution, let us know.

 

[Nealuss]

I really appreciate the replies. I just put a remanufactured ecm in about an hour ago and OD is back. I still one other little issue to figure out but now that I can drive it I can get to my buddies shop and get his expertise and scan tool on it.

As for future tuning I am probably done with any performance modifications until I build a motor, and I will go standalone at that point. I have considered an OBD2 swap, but at the end of the day it wouldn't be worth it vs. something like a Holley Terminator, Link, etc. With standalone the options are endless.

 

[ViolentMouse]

What is the other issue? if you don't mind

and yes, stand alone is the answer.

 

[Nealuss]

What is the other issue? if you don't mind

and yes, stand alone is the answer.

It idles fine, and runs fantastic going down the road, but wants to stall out when coming to a stop or when blipping the throttle. I may have a loose wire or pin, or it could be in the IAC. I put a new TPS in while diagnosing the OD issue because why not and it was OEM at 300+k miles. I'm leaning toward a loose wire because I can hear a motor turning sometimes when I jiggle the harness and I think it's the IACV. My buddy is a master diag tech and has all of the OBD1 Chrysler adapters we need to plug into my old truck. Only reason I didn't have him check it out before now is his shop is 45 minutes away and 4.10 gears +70mph = 4000rpm lol. We are going to check it out this weekend while doing a nice brake upgrade.

As for the standalone, Hemifever is local to me so I may see what he recommends. Not alot of Mopar tuning in my area (plenty of GM and Ford tuning though)

 

[ViolentMouse]

Sounds like you are on the right track. one of the only reasons I always suggest at least an obd2 ECM upgrade is for the ability to use affordable scan tools so you don't have to drive 45 minutes lol.

 

[Dan98]

It is possible to add toggle switches for manual lockup and overdrive. Sounds like you found the wires to the pressure switch and govenor now short them to ground and you get od and lockup. Modify the valve body to achieve lockup in second third and od. TRANSGO has literature on the 48RE
It will work on 46 or 47 Re too. View attachment Torque Converter Lockup Switch.pdf

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