I have a 2 wd, 2002 3/4 diesel. Automatic w/ OD. No additions.
At startup, the diagnostics show that the transmission input speed sensor is not showing up. This is causing the turbo to not be allowed to spool up. 2000 rpm max. After it does shift, sensor is picking up and everything runs good. As long as engine is running, no problem. Kill engine and problem starts again. Can unplug all three PCM connectors and will sometimes reset.
Have had transmission overhauled, changed VP44 pump, lift pump. Resently changed PCM, same problem. Changed Input sensor. Didn't fix.
I hate to spend $1600 for new ECM if not the problem.
Don't know where to look or ask... Don't trust Dealerships

 

The 48RE doesn't have a transmission speed sensor, perhaps you mean Engine speed sensor?

Does it throw a code? If so, what is the code shown.

Also, who diagnosed and did all the previous work?

 

1st- I'm sorry for posting in the wrong location.
2nd- A local diesel shop replaced the Injection pump after getting the common VP44 alarms.
3rd- Another local engine repair shop did the diagnostics. I really trust the mechanic. He has been building and racing cars for years. He has a long background in engine repairs. He put my truck on a engine diagnostics and took my truck for a drive. He showed me the sensor showing no indication until it shifted. It showed a primary and secondary speed sensor. The secondary speed sensor read constantly. Like I said, after shifting to second gear, the primary sensor started reading an RPM. Everything started working OK. The primary sensor may have been the engine output sensor. Can the ECM be having a problem like this?

 

Ok, yes, your 2002 does have 2 sensors, nothing to do with the Transmission though. You have a Camshaft Position sensor ( CMP ) and a Crankshaft Position sensor ( CKP )

There are a couple of possible things, 1.) Sensor 2.) Tone ring 3.) Wiring and 4.) ECM

First, can you identify the sensor that is not reading by it's correct function? I do know the tone ring on the crankshaft can go bad, I remember one of our members having to have it changed ( Ed, AKA Shovelhead ).

AT this point, I would say the ECM is the least possibility.

One thing that you really should do, get yourself a factory service manual from Genos Garage, 35 bucks on CD and it will save you thousands......

 

Thanks for the advice.
I changed the sensor. It gave the same results. What I don't understand is the logic of it not seeing the speed until it shifts and then reading fine. Seems to me, somewhere in the program logic, it can't read until something else kicks in. I don't know how the logic of all the speed, pressure, temp., is interconnected.
Will the service manual show all the systems and how they work together. Such as, temp. has to be xx degrees before it will allow the turbo can spool up.. etc...
Thanks again for the reply and I will take your advice and get the service manual.

 

Are you reading the PCM or the ECM? When you say the Turbo will not spool, 2000 RPM max, what exactly are you saying?

In other words, take us through the conditions as it gets to that shift, does it start normally, any codes present, will it free rev out of gear, how about acceleration up to that shift, etc.

This is a pretty basic dumb system, as far as electronic diesels go.....

 

This is what is confusing me totally.
The truck starts fine. Runs smooth. You can run it up past 3000-4000 rpm in park. Peg the RPM's if you want. You put it into gear and it runs up to 1800-2000 RPM. It acts/feels like it shifts into another gear around 1800 rpm. But at this point, it won't go any higher. The engine will speed up and slow down like normal. The turbo boost pressure won't come up, at all. It's like the turbo is kicked out.
It stays like this. At times, I have been able to unplug the 3 connectors on the PCM (on the firewall) and sometimes it will work fine until I kill the engine and the problem starts all over. I have a OBDII. It doesn't show any codes what so ever. Like I said earlier, the shop showed the primary speed pickup not reading anything until it shifts into second gear and then everything works fine. I can't understand why it won't read the primary speed sensor and not show some type of code. I agree, that this should be straight forward. Either it works or it doesn't. It shouldn't work both ways.
Note: when it does start reading the speed sensor, after shift, it is a steady reading. It doesn't cut in and out, like a faulty or dirty sensor, or short.

 

Ok, we can eliminate the ECM for sure, not absolutely the PCM though. I do believe the only thing transmitted to the PCM from the ECM is the crankshaft position pulse and the APPS signal.
The Turbo is dumb, the only thing controlling it is the amount of exhaust gasses and the wastegate, so if it won't build boost it is either a intermittent boost leak ( assumes you have good boost when it running normal ) or a lack of fuel to create the gasses.

Just for grins, have you done an APPS reset?

I wish some of the 24 valve guys would jump in here, I am quickly running out of my knowledge base of the 24 valve......

 

Side note: I purchased a reman. PCM. I thought that this had to be the problem. It is doing the same thing as the old one. Seems to shift better than the old but that's just a plus.

What is the best way to do a reset on the APPS? I've removed all the power from both of the batteries and left overnight.

I've taken the truck back to the transmission company that overhauled the transmission and he went thru a complete diagnostics. Didn't find anything wrong. So I ruled that out.

Could the mechanic possibly have changed the crankshaft sensor instead of the camshaft sensor? I didn't actually watch them change it. I did get the old one though.

I'm looking for anything here.

I understand about running out of knowledge base on this truck. I've talked with just about every mechanic I can find and they keep coming up empty.
I really appreciate the feedback that you've given.

It's hard to believe that someone out there hasn't had this happen before.

 

APPS Reset Procedure
This procedure has shown to help 24 valve ISB engines. It is basically teaching the fly by wire accelerator on these trucks to reread the position of the pedal and it's limits. Most complaints this will help with is poor acceleration, improper shifting, bucking in 5 and 6 speeds. Has been known to increase fuel mileage in some instances.

1. Set parking brake
2. Disconnect negative battery cables on both batteries
3. Turn ignition key to run(to drain any remaining capacitors)
4. Let truck sit for 30 minutes( this is the recommended minimum)
5. Return ignition to OFF position
6. Reconnect both batteries and secure, not a timed event
7. Turn key to run position(not start) and depress accelerator pedal slowly all the way to the floor
8. Allow pedal to return to top position slowly
9. Turn ignition switch OFF
10.Release parking brake

Found by a search..

 

Another APPs procedure found from search..
Written by Tyler (BigBlue)

Many have found that correcting the output voltage from the APPS sent to the PCM has increased the throttle response, and boost. This calibration also adjusts the APPS for wear.

Instructions:

Tools: Digital Volt Meter, T-20 Torx bit, #1 phillips, 10mm socket

With the key on, engine off you need to probe the APPS wire to see where the voltage is currently set at.
The best location to probe the wire is on the PCM (Power Control Module) which is located on the passenger firewall behind the air intake.
You want the C1 connector, this is the connector closest to the engine
You want the orange wire with a dark blue tracer which is pin #23 (Please use a suitable backprobing adapter for your meter lead, do not pierce the insulation as this can lead to water intrustion/corrosion.)
Voltage should be somewhere around 0.5 volts,
At this point the voltage reading does not matter, it just has to be accurately written down for later reference

TURN THE IGNITION OFF ON THE TRUCK

Remove the black plastic cover off of your APPS. There are two plastic screws. One on the top and one on the front facing the radiator. It takes a little prying to pull it off.

Undo the 6-10mm bolts that hold the bracketry in place but DO NOT REMOVE THE CABLES!!

You will notice the APPS is on the back of the bracketry that you just removed, it is held in place by 2-T20 torx bit screws. These screws have a little bit of locktite on them so make sure you have a good socket and gently give a little tap with a hammer before attempting to loosen. Be very careful because these screws strip VERY easily and you only get one shot at them (VERY VERY VERY IMPORTANT; They are VERY tight).

On the APPS you will find a white tag that gives you the information on what the APPS voltage should be.
After loosening the screws (do not remove) you can rotate the APPS clockwise or counter clockwise to get the adjustment (towards the front of the truck increases voltage and towards the rear of the truck decreases voltage)
The reading you took at the beginning of the process on pin #23 should match the white tag on your APPS. If it doesn't the adjust accordingly.

 

I beg to differ with some of the other replies above.

My 2002 service manual shows three relevant sensor inputs to the PCM:
1) Connector 1 Pin 8 ~ Crankshaft position sensor signal
2) Connector 2 Pin 27 ~ Vehicle speed sensor signal
3) Connector 2 Pin 28 ~ Output speed sensor signal

Although (in the manual) the crankshaft position sensor is shown as an input to the PCM, there is no such sensor in model year 2002.
There is a camshaft position sensor, but it's an input to the ECM, not the PCM.

The output speed sensor is located in the overdrive gear case.
It is positioned over the park gear and monitors transmission output shaft rotating speed.

Even though the diagnostic machine shows the signal is absent, and then appears upon a shift into second gear, you don't know if it is absent because the sensor is not outputting signal, or because the PCM is not processing the signal. This is because the diagnostic machine gets its information from the data bus on the PCM, not from the signal coming from the actual sensor.

So, you should monitor the actual sensor signal (connector 2 Pin 28 Light green / Black wire) and you will know better why the signal is absent. If it is not getting to the PCM, the problem could be a bad sensor, a bad wire, or something inside the overdrive gear case. Since the transmission was overhauled and the problem is consistent with a second gear shift, I would guess the highest probability is the latter, a transmission problem.

The 2002 service manual says that in the 46RE and 47RE transmissions, the output speed sensor signal is sent to the transmission control module and "shared" with the PCM.

That implies that maybe a TCM processes the signal before sending it on to the PCM.
However, I think the TCM was discontinued in the 1996 model year and was replaced by the PCM.
So much for the accuracy and trustworthiness of Dodge factory service manuals.
What transmission do you have?

Drew

 

Our trucks have no TCM.......... PCM does all trans functions.