Engine/Transmission (1998.5 - 2002) Interesting issue involving Cluster B fuse.

[BigPapa]

I have had an interesting issue with my new-to-me '98 24V auto.



If I remove the Cluster B fuse from the fuse panel in the dash or drive the truck with this fuse removed, the tranmsission takes off in 3rd gear, will not shift into OD or TC lockup, fuel gauge doesn't work, and the alternator doesn't charge.



I don't have a scanner so to "fix" it, I have to disconnect the batteries for @ 30-60 minutes then drive the truck 2-3 miles up to highway speed, shut it off, and do it again and again, 3 times total. After this everythings back to normal. I feel like if I had a scanner to clear the codes I wouldn't have to do the previous procedure to reset.



I found all this out the hard way, from experience. The Auto Meter pyro that came in the truck, uses a fuse tap that was plugged into the Cluster B spot in the fuse panel. I removed it with the truck running trying to figure out why the pyro didn't work.



Can anyone explain this to me? I just want an answer, I don't plan on removing any more fuses with the ignition switch on.



Thanks,

Scott

 

[Cosmo]

Without looking up what all is serviced by the cluster B fuse, I'd wager that you're killing a circuit that is important to the TCM, which causes it to go into limp mode.

 

[PBJ2500CTD]

OK... define the Cluster B fuse. I dug out my trusty 98 service manual and cannot find any reference to a "Custer B" fuse in the schematics. All the fuses in the junction block are numbered. Although there is a fuse B in the PDC that supples the Combination Flasher circuit.

 

[BigPapa]

OK... define the Cluster B fuse.

Fuse 14 in the junction block, clearly labeled "Cluster B" on the diagram on the back of the cover. It powers pin 6 on Connector A of the instrument cluster which is "Hot at All Times". Pin 6 looks to be connected to the warning lamps for Low Washer, Overdrive Off, VTSS, and 4X4 (mine is a 2WD) and the "Solid State Gauge and Indicator Drive Module" in the cluster.



Scott

 

[PBJ2500CTD]

Thanks Scott. Fuse 14... That is indeed the instrument cluster B+ fuse which feeds the items you identified. Now to just figure how it causes your issues...

 

[cerberusiam]

Pin 6 looks to be connected to the warning lamps for Low Washer, Overdrive Off, VTSS, and 4X4 (mine is a 2WD) and the "Solid State Gauge and Indicator Drive Module" in the cluster.

There is your answer, VTSS or vehicle transmission speed sensor, aka output shaft speed sensor. Lacking a signal or invalid operation the PCM goes into limp mode which is generally 3rd gear starts and no OD.



If you put a scanner on it or use the key trick you probably will get a P1740 or something on the order that is a companion code indicating more codes exist in the PCM.



Lacking a scanner to clear the code, it takes x amount of good starts to reset the PCM.

 

[PBJ2500CTD]

There is your answer, VTSS or vehicle transmission speed sensor, aka output shaft speed sensor. Lacking a signal or invalid operation the PCM goes into limp mode which is generally 3rd gear starts and no OD.

If you put a scanner on it or use the key trick you probably will get a P1740 or something on the order that is a companion code indicating more codes exist in the PCM.

Lacking a scanner to clear the code, it takes x amount of good starts to reset the PCM.

That's what I initially thought until I followed the schematic. Fuse 14 seems to be the power source for certain indicator lamps. The VTSS reference is for the Vehicle Theft Security System lamp which is controlled by the CTM (Central Timer Module). I sure whsh the schematics had the "black box" circuits included so a review of the signal processing could be made. The instrument cluster is scattered over several pages, but nothing readily found tying the issue noted with the fused circuit.

 

[cerberusiam]

What exactly is this "Solid State Gauge and Indicator Drive Module"???



Somewhere pulling that fuse is powering down the output shaft speed sensor and\or the gov pressure sensor circuit and or the transmission control relay.

 

[PBJ2500CTD]

Same thought here. A drive module usually supplies the voltage to power or "drive" the analog gauges. As far as I can tell the gauges do not have an output that provides feedback to any other circuit; although a couple of wires head to the PCM - but they appear to be outputs from the PCM. That's why I wish the schematics had more detail when a wire goes to a "black box". It's gotta be there somewhere.

 

[PBJ2500CTD]

Looking closer to the instrument system I come up with two questions;

1. Where does the CCD (Chrysler Collision Detection) data bus get its power? Is it powered through the PCM?

2. Is there a feedback circuit sending positional data back to the CCD or PCM from the effected gauges?

 

[BigPapa]

Well, she's back in "the mode". I didn't pull that fuse this time but we did remove the driver side battery. Right side battery was left hooked up so I didn't figure I'd lose power.



A little more to the story. This is a '98 24V truck with the 47RE auto. I have transplanted my '95 12V motor into it. We were initially running the 12V TPS, a 24V crank sensor on a properly toothed tone wheel, 24V oil pressure, intake air temp, and coolant temp sensors. All gauges work fine when not in "the mode". Tach, speedo, oil pressure, coolant temp, volt meter, and fuel gauge.



First drive it did this. No charging, taking off in 3rd unless manually shifted, no OD, no lock-up, no fuel gauge. This happened for the first few drives. The batteries wouldn't stay charged, so I took them both out for testing. They were out for a week and I replaced one which was bad.



When I put them in and drove the truck to the shop, it worked right. Charging, taking off in low gear, shifting like it should even into OD and it would lock up if you stay in the throttle, and the fuel gauge worked. The only issue was if you were not in the throttle, it would unlock.



I decided to put the 24V APPS on to try to solve that issue. Today we put the APPS on which also required swapping the throttle cable, cruise cable, and TV cable. To swap the cruise cable I had to remove the left battery and battery tray.



When we got it back together it was in "the mode". We scanned and cleared all DTC's. I unhooked both batteries and left the headlight switch on for 17 minutes, then drove it @ 5 miles, turned it off and restarted. I did this three times. The 3rd time the batteries were low enough it wouldn't start. Jumped it off and hot wired the alternator where it would charge, did the drive cycle again, and no change. I have the batteries disconnected now and will leave them that way for @ 1 1/2 hours and try again.



Will let you know how it does this time.



Scott

 

[cerberusiam]

Tie the negative battery cables together to completely discharge anything that is holding one. Should only need to do this for 30 minutes and can then hook things up and try again.

 

[PBJ2500CTD]

Scott,

A whole new can-o-worms now...

Did you write down the DTCs? They could be helpful.

Your symptoms indicate an intermittent circuit somewhere.

Did you re-connect the engine block to frame bonding strap when you swapped engines? How about the grouning points for the wiring harness, are they clean and secure?

Normally batteries should be changed as a pair as a weaker battery can pull down the better battery.
Check all of your battery cables for continuity. They should have less that one ohm.
Alternatively, you can hook up a jumper cable from the negative terminal of the batteries to the engine block, or bracket. If the symptoms are resolved you have a bad ground circuit.
Also, disconnect all three PCM connectors and check for corrosion or bent pins. Clean and reassemble.
Now, if you only had a PCM to swap out...

Best of luck!

 

[BigPapa]

Did 5 drive cycles tonight. No good, still in "the mode".



I have one of the best techs I've ever met helping me with everything. He is VERY meticulous with any and all electrics. He cleaned and checked all grounds, all PCM and ECM connectors. The PCM is the original with the truck. The ECM is supposed to be from another '98 24V auto.



I tried the key on-key off 3 times to check DTC's and it will not display anything. I'm planning to take it to a friend to scan DTC's Monday. There has always been, and always will be, DTC's present for Injector Pump and MAP sensor. I don't have either, will never have a VP, and have been told I do not need a MAP. As everything was working good, I would say this information is correct. There were 2 other DTC's present before, one was for Idle Validation and the other seems like was for something involving the APPS. I was not looking at the scanner today but was told there were 7-8 DTC's that were cleared and then came back immediately on key-on.



The only thing I can figure is there is something wrong in the wiring around the ECM and APPS connectors that I'm bumping. When it did this the other night, I had been adjusting the idle and of course today we were all over the wiring in that area.



The reason I didn't mention the engine swap earlier was that everything was working good for over a week until I either moved the wiring while adjusting the idle or it did something when I pulled that fuse. Since I did not pull the fuse today, I'm ready to rule that out.



Thanks for any assistance. I will advise with a list of DTC's when I find them.



Scott

 

[BigPapa]

Borrowed a scanner and read these DTC’s:



P1682 – Charging system voltage low

P1388 – Auto shutdown relay control circuit

P0743 – Torque convertor clutch solenoid /trans relay circuit

P1389 – No ASD relay output voltage at PCM

P0753 – Trans 3-4 solenoid/trans relay circuits

P0463 – Fuel level sending unit volts too high

P1492 – Battery temp sensor voltage too high

P0720 – Low output speed sensor RPM, above 15MPH

P0748 – Governor pressure solenoid /trans relay circuit

P1765 – Trans 12 volt supply relay Control circuit

P1693 – DTC detected in companion module

P0237 – MAP sensor voltage too low

P1689 – No communication between ECM and Injection pump module

P0222 – Idle validation signals both low



These are all present after going through 4 drive cycles as mentioned above. Cleared All DTC’s. These re-appeared:



P0463 – Fuel level sending unit volts too high

P1492 – Battery temp sensor voltage too high

P1765 – Trans 12 volt supply relay Control circuit

P1693 – DTC detected in companion module

P0237 – MAP sensor voltage too low

P1689 – No communication between ECM and Injection pump module



Cleared again. All returned except P1765.



Cleared again. Same list returned.



As mentioned, P0237 and P1689 are going to be there. I figure P1693 is from them. So I guess I’m basically dealing with P0463, P1492, and possibly P1765.



Scott

 

[cerberusiam]

P1765 is limp mode for the trans. Essentially stuck in 3rd gear, no lockup, no OD. You need a scanner that will read the PCM and see if you can figure out what is tripping that code if possible.

 

[BigPapa]

Any ideas from the other codes what could be causing it? I figure the transmission codes are from me driving it and shifting manually. The charging codes and possibly the battery temp code are probably where I had the alternator "hot wired" to force charging.



The fuel sender doesn't work when it's in "the mode", or is there a possibility the fuel sender is causing the issue? If the fuel gauge works, everything else works... ... hhmmmmm.....



Scott

 

[PBJ2500CTD]

... uses a fuse tap that was plugged into the Cluster B spot in the fuse panel.

Experience with fuse taps: depending on the type, the tap may have spread rhe fuse socket contacts enough to where a good contact with the fuse is no longer possible with the tap removed herefore causing intermittent operation.

And, why the forced charging? Is there a regulator issue, or no charging in the "mode"? Something in the harness or PCM seems to be intermittent.

 

[cerberusiam]

Any I figure the transmission codes are from me driving it and shifting manually.

No, doesn't work that way. Manually shifting and driving will not cause codes unless there is a source that the ECU can identify as a problem.



If this was a 3rd gen I would say either the FCM or TIPM was hosed. Not sure if the 2nd gens have a PDC that can burn circuits out.

 

[BigPapa]

The fuse tap actually looks like a good design. The tips that go into the panel are exactly the same size and shape as a fuse and then it has 2 fuses that go into it. I don't think it would spread the contacts any more than a fuse.



The transmission codes are what's got me stumped. This is the first time I've seen them and like I said, they appeared AFTER the battery removal/reset procedure mentioned.



The alternator does not charge when in "the mode". I had to drive @ 50 miles to the house after installing the APPS and the batteries finally got so low from driving with headlights and wipers on with no charge I had to get a jump and "hot wire" it to make it home. I've just hooked it up everytime since so I don't kill the batteries again.



I'm leaning toward an intermittent wiring or PCM issue.



Thanks for all the help. Keep it coming.



Scott