LSWRANGLER

Hi Gents,
I just got the Jeep back from the Dyno tuner yesterday. He said the PCM could not see what gear the transmission was in, so it was calculating its in gear idle force off of applied torque values.

I have a GEN III LS5.3 (L33) mated to a 4L60E (Single block PND connector).

I need to start testing but Im not sure where the PCM gets this info from. Is it simply the PND switch on the gear selector, or is it part of the valve body harness in the tranny? I want to check for circuit continuity first, before I dive deeper.

Any guidance would be most appreciated!

MontecarloDrag

iTrader: (3)

The current gear comes from the valve body thru the grey round connector on top of the transmission pan.
The other switch on the gear selector rod is for the position of the selector itself.
Both of those sensors can be logged with a scanner.
The valve body sensor sends the "TRANS CURRENT GEAR" or "TRANS RANGE" signal, it will change from 1 to 4 when transmission shifts.
The other sensor sends the "PRND STATUS" signal, it will change from Park, to Reverse, Neutral, D4, D3, D2 etc. depending to where you move the shifter.

The valve body position switch trips a DTC when not working properly

mrvedit

Sorry, but you are incorrect.
The sensor on the valve body, often called the Manifold Pressure Switch, is in the GM technical doco called the "Manual Valve Position Switch". It indicates which position the shifter is in. The "Hydramatic 4L60E Technician's Guide" documents this fully on page 37.
This allows the PCM to know what position your shifter is in.

The PCM does not need to be told what gear the trans is actually in because the PCM commands the gears. If the PCM commands a shift, but then does not see a Speed versus RPM change, it throws a code indicating a bad solenoid or slippage.

The switch on the side of the trans is optional, but if installed it often performs these functions:
1. Acts as the Park/Neutral safety switch to the starter.
2. Tells the PCM whether the shifter is in Park/Neutral or Drive/Reverse - the PCM then selects the matching idle tables to compensate for more engine load when in Drive/Reverse.
3. Acts as the switch for the backup lights.

Don't feel bad MontecarloDrag, lots of mechanics, if not the majority, make this mistake.

LSWRANGLER

Thank you Gentlemen for the replies. All good info. This will help me allot.

Yesterday I gave it a 100 mile road test. On the last 10 or so miles, it stopped shifting into 4th and would hang on to 2nd as long as I had any throttle applied. I had to let off the peddle, then it would shift into 3rd. 1st to 2nd is fine though.

It seems my troubleshooting just got deeper.

LSWRANGLER

Understanding this is not an PCM/Programming question, but wanting to stay with this thread, Would a overheated tranny cause it to not shift into 4th and for 2nd to hold on forever before going into 3rd?

I did check and no codes are stored. My PCM was reprogrammed and has had a few circuits turned off. I'm not for sure if the PCM will even report codes any longer after the program. I cant get a real answer out of the place that did the tune.

Just part of the diagnostics.

mrvedit

Do you have HP Tuners or other scanner that can show the commanded gear?
I don't know the answer to your overheated tranny question, but there is a separate shift table for "Hot"; not sure what temp triggers it.

Going back to "He said the PCM could not see what gear the transmission was in", this might indicate that the Manifold Pressure Switch (MPS) is bad. It is relatively easy to replace after dropping the pan. Your post #4 is not quite consistent with a bad MPS, but some of the strangest trans problems have turned out to be a bad MPS.

Are you absolutely sure your shifter and trans are in sync? If your shifter says [OD] (or [D4]), but the trans is half way between [D3] and [D4], you will also have strange problems.

LSWRANGLER

MR V,
I don't have HP Tuner or EFI live yet, all I have currently is Torque Pro on my tablet with a bluetooth OBDII adapter. It works nice, but cant have a conversation with the PCM deep enough to get the good info.

I agree with the MPS being a good possibility. This trans leaks bad as well as the other issues I'm having. A tear down and re-seal is in the works. After seeing the price of the solenoid kits w/ harness, I plan on changing out all the electrics in the process.

I think after the rebuild, I'll see how it performs and go from there.

I sincerely appreciate yours and everyone else s input on this.

mrvedit

Swapping out all the electrical parts is not expensive, requires only dropping the pan, and cures many problems. And, if the trans still needs a rebuild, tell the rebuilder you installed all new electrical parts and their price should come off the normal rebuild price.

MontecarloDrag

iTrader: (3)

Why would I feel bad, I have done countless trans swaps and they perform beautifully. I would care less about what others think about my feelings

How did He know the PCM isn't seeing what the current gear is? If he was tuning he must have HPTuners or EFilive. Ask him to test it with the scanner, datalog the PIDs I said in my previous post:
"TRANS CURRENT GEAR" should be 1 if you're not moving. Changes to 2, 3,4 when it shifts.
"PRND STATUS" changes from Park to Neutral, D4, D3 etc. when you move the shifter.
Take the truck to a little ride and test if this works as it should, it will be very obvious watching the scanner.

mrvedit

Excellent advice.
If your tuner doesn't know how to do this, find another one.
If the tuner is going to charge you $100+, it might be easier to replace all the electrical parts, especially the MPS, and hope for the best.

LSWRANGLER

The plan is to replace all the electrics and reseal the tranny. Then I may just pony up and buy HP tuner. Ive paid $500 for the initial program and dyno tune so far. Id could almost have the HP Tuner Pro paid for by now. Add the wideband O2 kit and Id' have a rolling dyno.

My tuner guy doesn't give the warm fuzzy's in his capabilities. I have a suspicion he disable trouble codes to kill the SES light. There have been several bugs Ive worked out in this swap that should have triggered codes, but yet none were logged. This one included.