Hey all,

Problem started with the trans yesterday. Drive fine for the first 4 miles or so, then got "stuck" in second gear. Did some research and tried to read ECM codes but I don't have a check engine light. I bulb is good, but the light doesn't (& never has since I had the truck) come on.

Questions:
Is it supposed to come on for a 93, or is it only for newer trucks?
Could it be related to the tranny problem?
What are the steps to check to get the trans fixed since I can't pull any codes?

Thanks,
- Shawn (in central Ohio)

93 dosnt really have any tranny codes, or a limp mode like the allison or newer transmissions. Time to get checked out and probably a rebuild.

Well that stinks. It just appears to just be "stuck" in second gear all of a sudden. Worked fine with no rough shifting or anything to indicate a problem.

Should there be a "Check Engine" light on the dash when you turn on the key (there ain't)?

Are there any steps that I can do to troubleshoot the tranny problem bofore giving up and taking it to a transmission shop?

- Shawn

Without checking codes it is difficult.
Does the problem happen all of the time or is it intermittant?
My TPS caused similar problems in my 93.
And yes, when you start the truck/turn the key on, there should be a check engine light that comes on.
Mark

I wanted to check the codes and that is why I started looking for the check engine light. I have not seen it come on in the time that I have owned the truck (6 months) so I just assumed that it didn't have one.

I pulled off the panel and sure enough there is one there. I replaced with a known good bulb, but it still does not light up when you turn the key on or try to check the codes.

The tranny stays in 2nd all of the time since it started yesterday.

- Shawn

Does not seem to be a good situation, although may not be as bad as it seems. There are several guys on here with vast knowledge and may be able to point you in a better direction.
Sounds like you may have a wiring issue.
One thing I have found about these diesels(and I am new to them too(1 year now)), is that the strangest thing may cause alternative problems.
I will try to point some others to your thread. You have the same truck as mine and I have learned alot on this and another forum.
Mark

Here is a list of the codes for that trans, but you need to get the check engine light to work, or get something to scan the computer.


DTC 21 - Throttle Position Sensor (TPS) Circuit (High Sig.)
DTC 22 - Throttle Position Sensor (TPS) Circuit (Low Sig.)
DTC 24 - Output Speed Low
DTC 28 - Pressure Switch Manifold, Illegal Combination Detected
DTC 39 - TCC (http://www.alldatapro.com/alldata/PRO~V596348~C6937~R0~OD~N/0/41746052/42417677/42418599/42418651/34853741/34857029/56218937/56492733) Stuck "OFF"
DTC 53 - System Voltage High
DTC 58 - Transmission Temperature High
DTC 59 - Transmission Temperature Low
DTC 68 - Overdrive Ratio Error
DTC 73 - Force Motor (http://www.alldatapro.com/alldata/PRO~V596348~C6937~R0~OD~N/0/41746052/42417677/42418599/42418651/34853741/34857029/56218937/97115103) Current
DTC 75 - System Voltage Low
DTC 81 - Shift Solenoid (http://www.alldatapro.com/alldata/PRO~V596348~C6937~R0~OD~N/0/41746052/42417677/42418599/42418651/34853741/34857029/56218937/56514627) "B" Circuit Fault
DTC 82 - Shift Solenoid (http://www.alldatapro.com/alldata/PRO~V596348~C6937~R0~OD~N/0/41746052/42417677/42418599/42418651/34853741/34857029/56218937/56514627) "A" Circuit Fault
DTC 83 - TCC Solenoid (http://www.alldatapro.com/alldata/PRO~V596348~C6937~R0~OD~N/0/41746052/42417677/42418599/42418651/34853741/34857029/56218937/56492733) Circuit Fault
DTC 85 - Undefined Ratio
DTC 86 - Low Ratio
DTC 87 - High Ratio

Check cigaret lighter fuse., also check trans fuse in the fuse block. If they are good, get a scan. Could also be ignition switch.
mike

When my '94 was getting stuck in 2nd if I shut it down and restarted it it would act right for a few minutes to a few days. I changed the input and output sensors and haven't had anymore problems in a couple years now since. $30 each x2 is better than getting hustled into a rebuild at Aamco, not that I'd even let them work on my skateboard.

Did you buy the truck used, if so, could be someone disconnected the trouble light. One problem with the tranny could be a sticking valve. If thne fluid hasn't been changed in a while, that might help . If you change the tranny fluid, change the internal filter to.And worst of all, you might need a rebuild.

I bought the truck several months back with a broken crankshaft. I rebuilt the bottom end and it has been running fine ever since.

So far, here is what I have learned:
Check electrical connections & grounds (battery too)
Check wiring for breaks & chafing
get codes read (if possible)
change fluid & filter

Any other suggestions before I tear into it again?

Thanks
- Shawn

Status report:

Took to repair shop to have the codes checked. The little Snap on scanner said it could not communicate with the trucks ECM. That can't be good.

Checked all electrical connections I could find, cleaned grounds.

Dropped trans pan, replaced both shifting selonids and shaft sensors ($60), filter & fluid.

Still stuck in second gear.
This really sucks.

Shawn,
Don't be discouraged by the fact that the readout they received was could not communicate. I've learned that this is typical with a 93 since I have one. I go to Advanced to have them put their scanner on it and while they are waiting to get the message on the unit they use, I watch the blinks on the check engine light(which unfortunately yoy can not do right now) and get the codes that i need to see or none at all. When they turn around to tell me that it is not reading any codes, I've already written anything that comes across it via the check engine light. It's an easy way of doing it without using a paperclip on an OBDI.
I agree with the guys that replied to your thread earlier stating that you need to get your check engine light working prior to following up on any other problems. It may something simple and if you continue to follow up on different issues without codes, it can cost you an arm & a Leg. Personally, I can not afford that.
Mark

You have an electrical problem. This trans goes to 2nd when it has no power. If the ECM fuse is okay, you may have a computer problem, especially since you said the check engine light doesn't work. A few years ago my '91 had a fuel pump short out and blow the ECM fuse. It was running on LP at the time, so the engine didn't quit, but the trans went to second. Both shift solenoids are off in 2nd, it is a limp gear to get you out of immediate trouble.

Updated status:

I bought a PCM (I think) from a junkyard on the way home. Part # 16147609
I have heard it called the ECM, PCM, and the transmission control computer.

Plugged it in and nuthin but $50 poorer. No transmission shifting and no check engine light. I checked for voltage at the TPS looking for the 5 volts and there is nothing.

I don't know if this is even related to the transmission problem.

Where could I find a wiring diagram for a 93 turbo diesel truck?
There is 12v going to some of the wires that go to the computer, but it doesn't seem to be going on out to the sensors and transmission.

Any ideas at all?

You need to quit guessing and throwing parts at it. All you're going to accomplish is emptying your wallet.

Get that Check Engine light fixed and go from there. If you can't get it working, take it someplace that can. Then the computer will point you in the right direction.

Sounds to me like your truck is in limp mode. I'm about 95% sure of it, and I seriously doubt your tranny needs a rebuild.

Clear the codes! autotrannies stay in limp mode as long as dtc's are present. I've seen this happen from a bad alternator, or bad A shift solenoid (on the vavlebody).

the fact that you have no check engine light and no comunication with pcm and no shift and no 5 volt ref to me means you have a pcm issue and you have replaced it means it is a wiring issue if your pcm is shut down you will have all of these problems the engine will run fine because it is not computer controlled on a 93 you need a wiring diagram to check all the power inputs and grounds at pcm first thing to chack is for power at trans 12v at the pink wire terminal e on the trans harness this comes fromthe trans fuse if there is power there the pcm is not grounding the solenoids you can do this manuely if you want to verify the trans they are the the lt green and yellow blk wires at the trans i believe terminals "a" and "b" after that you will need a wiring diagram to get the pcm working again

First get the 1-2 and 2-3 shift solenoids the go into the back of the valve body and only cost about $20 each. Common problem on those units to loose third or fourth due to solenoid hydraulic leak with no codes. Hope this helps.:D

If you have a tps issue, always address that first with transmission work.:D

http://www.atraonline.com/manuals/general/tetdv/tetdv-toc.htm

? may help

The solution appears to be the fuel pump relay.

I think there was a short in the relay that caused the fusible link to blow that feeds the ECM/TCM/TCC (whatever you call it). Every time the engine would start up, the fusible link would blow again.

As I understand it, as the oil pressure comes up, the power to the lift pump is supplied through the oil pressure switch. That circuit was shorted out in the relay.

New relay - $12 at autozone and things are working again. I even have a "Service Engine Soon" light now so I can get codes!

Thanks to everyone for the help!

- Shawn

good to see you got it fixed !! i knew it was the pcm shut down:muahaha:

Any time a 4l80e goes to limp mode you can reset it by pulling the trans fuse for 10 to15 minutes or disconect the ground cable for that long, that wont fix the original problem but it will get you going so you can watch it some more, it is usually a power supply that causes the default.