48RE, Limp Mode, No Codes

[lgjohnson]

Hi,

My '03 3500 CTD SRW has 94K and has been runnin' fine. transmission fluid changes every 30K, etc. Went to leave from work last night and noticed the gear indicator light would not light up around R, D, 2, 1 ... only P and N would light. Then I noticed that it was in limp mode with only 3rd gear.

I'm not getting any codes at all.

I'm thinking the pressure modulator and/or governor solenoid may have crapped out, but I thought those things would toss a code if they went bad.

I pulled the wiring terminal plugs on the ECM to make sure they were tight and dry as we've had alot of rain the past couple of days. They were fine.

Anyone have any ideas what might be causin' this? Thanks. LJ

 

[lgjohnson]

UPDATE: Well, it wasn't the pressure sensor/governor solenoid (didn't think it would be with no codes present). Either I have "shot" transmission or the PCM is bad. Need to narrow it down somehow. Any suggestions, guys?

Thanks.

 

[04 Diesel Power]

Wish I could help, Good luck.

 

[Jobrated]

My transmission did the same thing @ 66K -- the dealer replaced the Valve Body claiming something, probably a metal shaving, must have come loose during the 65K Transmission Fluid change and became lodged in the valve body.



Grant

 

[lgjohnson]

Dealer wants to pull the whole transmission and tear it down...
I said, "no" and going to go pick it up this afternoon.
I'm the only one that has ever serviced that transmission and there has never been any indication of fluid burning, metal chips, etc. Just the standard fine mud around the magnet.
I think I may have a stuck piston in the valve body. I may go with a DTT valve body on this thing. Anyone ever use one of their "tow style" valve bodies in a stocker?

 

[Lightman]

UPDATE: Well, it wasn't the pressure

sensor/governor solenoid (didn't think it would be with no codes present). Either I have "shot" transmission or the PCM is bad. Need to narrow it down somehow. Any suggestions, guys?

Thanks.

Here is something you might try My truck is a 2004 not a 2003 so it might be different look in the fuse box by the battery my transmission relay is # 59

remove the relay and make a jumper wire and plug it in the relay socket where pin 30 and 87 from the relay plug in this will bypass the computer control of that relay and see if your transmission works also check fuse #5 and 50 they are the transmission fuses.

 

[lgjohnson]

Here is something you might try My truck is a 2004 not a 2003 so it might be different look in the fuse box by the battery my transmission relay is # 59
remove the relay and make a jumper wire and plug it in the relay socket where pin 30 and 87 from the relay plug in this will bypass the computer control of that relay and see if your transmission works also check fuse #5 and 50 they are the transmission fuses.

2003 and 2004 apparently are identical. I checked the service manual and then went & looked for em. I swapped the fog light relay (known to be working) and the transmission relay (same part#) to no avail. I then checked fuses #50 and #5 and they looked fine (not blown). I even swapped with them other fuses of the same amperage. All to no avail. I then pulled the relay back out and checked for voltage (with the key in the run position) at the proper relay terminals (30 & 86) and they had voltage. I placed a jumper across 87 and 30 just to make sure and LOW & BEHOLD my gear indicator lights are working with the jumper in place!!!
I've got voltage at 86 so I'm wondering why the relay won't pull in??
A BIG Thanks, Lightman!! Now, I just need to figure out why relay isn't pulling in. .

 

[cerberusiam]

Hi,

My '03 3500 CTD SRW has 94K and has been runnin' fine. transmission fluid changes every 30K, etc. Went to leave from work last night and noticed the gear indicator light would not light up around R, D, 2, 1 ... only P and N would light. Then I noticed that it was in limp mode with only 3rd gear.

I'm not getting any codes at all.

Would be interesting to see if the range select module could cause this issue. You could wire a switch into the OD and verify if the mechanical portion works. That should tell you if it is electronic or mechanical.

 

[cerberusiam]

Hi,

My '03 3500 CTD SRW has 94K and has been runnin' fine. transmission fluid changes every 30K, etc. Went to leave from work last night and noticed the gear indicator light would not light up around R, D, 2, 1 ... only P and N would light. Then I noticed that it was in limp mode with only 3rd gear.

I'm not getting any codes at all.

Would be interesting to see if the range select module could cause this issue. You could wire a switch into the OD and verify if the mechanical portion works. That should tell you if it is electronic or mechanical.

 

[lgjohnson]

I updated Post #7. By jumpering the transmission relay, everything comes to life. I just need to figure out why this relay isn't pulling in. I have voltage to its coil so something is up with the PCM ground. Could be just the plug isn't pushed in all the way or there might be some corrosion on that particular pin. Too late for me tonight to mess with it, but I will later on this week.
A BIG thanks to Lightman for this one...

 

[Lightman]

I updated Post #7. By jumpering the transmission relay, everything comes to life. I just need to figure out why this relay isn't pulling in. I have voltage to its coil so something is up with the PCM ground. Could be just the plug isn't pushed in all the way or there might be some corrosion on that particular pin. Too late for me tonight to mess with it, but I will later on this week.

A BIG thanks to Lightman for this one...

The PCM grounds that relay that is how it puts the trans in limp mode by opening the ground to it

 

[lgjohnson]

Thanks Lightman...
IF it isn't corrosion or moisture on that pin, I guess its the PCM. I will check that point in the terminal of the PCM and see if it goes to ground... which if it doesn't, would indicate a bad PCM.
Ever change out a PCM? Looks like a straight bolt-in, but I think the truck's VIN and mileage need to be programmed into it. Now, I need to find the best source for a PCM if it proves out to be bad... .

 

[F-15I Ra'am]

Thanks Lightman...

IF it isn't corrosion or moisture on that pin, I guess its the PCM. I will check that point in the terminal of the PCM and see if it goes to ground... which if it doesn't, would indicate a bad PCM.

Ever change out a PCM? Looks like a straight bolt-in, but I think the truck's VIN and mileage need to be programmed into it. Now, I need to find the best source for a PCM if it proves out to be bad... .

You might wanna check if the PCM is covered under the 100k warranty.

 

[Lightman]

When you say there are no codes have you check it with a scanner or just key on off 3 times you might want to check it with a scanner. I dont think it sets the check engine light

 

[lgjohnson]

When you say there are no codes have you check it with a scanner or just key on off 3 times you might want to check it with a scanner. I dont think it sets the check engine light

Lightman, You're correct: it has not set the "CEL" at all. However, I've checked with both the "key dance" & my scanner; I've got no codes on several tries. I will hook up my scanner again this evening just to make sure before I do anything else.

 

[lgjohnson]

You might wanna check if the PCM is covered under the 100k warranty.

Did that yesterday..... 'Naaaaaaa' as in the AFLAC Insurance goat. #@$%!

 

[Lightman]

With the relay removed it will show a code I don't remember the number

 

[PBrauer]

The transmission range switch ON THE TRANSMISSION is what drives the indicators in the instrument panel. So far, nothing in the thread has ruled out a simple defective switch. It's the only thing that tells the ECM/PCM what gear/range you've chosen with the "shifter"... The transmission itself is controlled "mechanically" by the position of the lever AT THE TRANSMISSION... . The "switch" tells the ECM what position that lever is in. There are no switches or sensors in the steering column. It makes sense that the most likely failure "mode" (from an open contact in the switch) would be Park or Neutral.

Even if you had a problem with the transmission, the indicators in the instrument panel would still follow the switch. Good chance you nailed the problem in your first post...

Before you replace anything expensive you should at least test all positions on the switch with a meter. It's not an expensive part either. Fairly easy to replace.

Good luck.

Edit:
PS... I don't think you're actually in "Limp" mode, just a default valve body "alignment" (gear) with the clutch(s) engaged by the shift lever... PCM thinks the trans. is in Neutral...

 

[lgjohnson]

The transmission range switch ON THE TRANSMISSION is what drives the indicators in the instrument panel. So far, nothing in the thread has ruled out a simple defective switch. It's the only thing that tells the ECM/PCM what gear/range you've chosen with the "shifter"... The transmission itself is controlled "mechanically" by the position of the lever AT THE TRANSMISSION... . The "switch" tells the ECM what position that lever is in. There are no switches or sensors in the steering column. It makes sense that the most likely failure "mode" (from an open contact in the switch) would be Park or Neutral.



Even if you had a problem with the transmission, the indicators in the instrument panel would still follow the switch. Good chance you nailed the problem in your first post...



Before you replace anything expensive you should at least test all positions on the switch with a meter. It's not an expensive part either. Fairly easy to replace.



Good luck.



Edit:

PS... I don't think you're actually in "Limp" mode, just a default valve body "alignment" (gear) with the clutch(s) engaged by the shift lever... PCM thinks the trans. is in Neutral...

See my post #7: After jumpering the relay, everything powered up and started working properly: gear position indicator lights and transmission as well. So the gear selector sensor must be powered thru that relay as well. The PCM is definitely not making a ground for the relay coil. Could be moisture/corrosion on the connector pin, or a loose pin or a broken wire or just a bad PCM.

I will check for codes, wire continuity and grounding tonight. Then check the connector for moisture etc. This truck has had the TSB done that added the o-rings to the connectors to prevent moisture intrusion, but it can still get by em, especially down here in south Louisiana. We had a heavy rain the day before it went bad... . I suspect moisture.

I appreciate the responses and will keep ya all posted to my findings... . hopefully, its just something simple and it will be back running good again. IF it is, in fact, the PCM or a broken wire I will likely go with the parts listed in the 2nd part of that TSB (upgraded harness and PCM) and "kill two birds with one stone".

 

[lgjohnson]

UPDATE: Checked for wire continuity from relay 59 (pin 85) to the C2 (pin 30) and it was good and solid. Checked the corresponding pin on the PCM side, which should be ground (with the key on) and it was open showing no ground at all. I do believe this pretty much confirms that the PCM is bad.



/rant on: BTW, when you look at how the o-rings are supposed to work from TSB# 08-031-03, it looks like it can still leave a pretty weak seal for the PCM connectors, especially here in south Louisiana with the rains we get. I suspect I got water in there during that last heavy rain we got and it did it in. IMHO, the proper solution is to do the PCM and harness upgrade that makes up the 2nd half of that same TSB. This was updated again, in detail, in the Customer Satisfaction Notification# C42 dated February 2004 but I guess that would have cost DC a small fortune for THEIR mis-design.

Also, the service at the local dealer was absolutely the pits. I took that truck in there and specifically asked them to check the PCM. When I started checking fuses/relay etc. , the road dust on the fuse box cover was totally undisturbed as was the connectors to the PCM... . nobody even looked at it yet they wanted me to sign off on pulling out the transmission for a complete tear down and rebuild... . naaaa, I wasn't falling for that deal. \rant off



I'm going to order the updated PCM and harness next week and install it myself. I believe the truck will run fine, but will likely toss a code. I will take it to the dealer in Lafayette or Baton Rouge and have the VIN/mileage entered in and flashed. I'm done with the local dealer here for ANYTHING, including my next new truck.