Engine/Transmission (1998.5 - 2002) very confused, please help

[nathan saunders]

So I was driving down the road the other day and the check gauges light came on in my 02 Cummins. The voltage gauge said it had no charge. At the same time, my transmission messed up. It's and auto and takes off in 3rd gear. I can manually shift second but no first or overdrive. I bench tested the alternator and its fine. Also replaced the batteries. What's goi g on with my truck?

 

[fox]

Read the codes.
I can think of several causes.
Get back to us after the codes are read.

 

[nathan saunders]

Ok so there are no codes that are being thrown. The check gauge is not always on .I don't know if that has something to do with it.

 

[SAndreasen]

check your grounds and ground cables

 

[JR]

The transmission malfunction is likely voltage related so I wouldn't worry about looking into it until you get the charging system figured out.
How did you test the altenator?

 

[nathan saunders]

I just had it bench tested had two different places test it four times. It tested good every time

 

[JR]

Start your truck and put a voltmeter on the output of the altenator. What is the voltage reading? Need to determine whether or not it is actually charging while on the truck.

 

[seafish]

The first thing that you need to do is to check EACH and EVERY battery terminal connections and also the main ground/body connections for being CLEAN and TIGHT.

Then you need to check the conditon of the battery crossover cable (large positive) that runs between the two batteries...it tends to corrode BENEATH the insulation, just a few inches back from the batteries, and this corrsosion can and will lead to erratic battery volatges, which in turn will lead to corruoption of sensor and ecm oltage and function. Let me repeat this, a poor condition xo cable leads to all sorts of seemingly random problems due yo voltage fluctuations outside of the systes design tolerances. Once these items are checked off the list, you can proceed with other battery diagnostics, but these must be done first to ensure an accurate diagnosis of the charging system simoly because they are crucial/itegral to the proper operation of the charging system, as well as the operation of the trucks ecm and various sensors.

 

[seafish]

I just had it bench tested had two different places test it four times. It tested good every time

see my post above, bench testing the alternator or evn the batteries in a dual battery system does not tellt he whole story and will not ensure that the charging system is in fact working properly...you must also check the cables connecting them, as tehy are part and parcel to the charging system.

 

[nathan saunders]

Ok thank you for your help .I will check the xo cable and see what it looks like. Otherwise all other cables and connections have been cleaned and checked

 

[seafish]

Ok thank you for your help .I will check the xo cable and see what it looks like. Otherwise all other cables and connections have been cleaned and checked

IMO, the easiest way to check the xo cable is to is to check battery voltages with the xo cable removed…they should be very close or equal to each other…unequal battery readings (with the xo cable removed) heavily indicate a xo cable problem while equal battery voltages would tend to indicate a properly working xo cable and charging system. If you need to visually confirm a problem with the xo cable, you can slice the insulation from the battery terminal along the length of the wire for about 4", then peel it open to look for corrosion or oxidation. If it looks good, simply close the insulation wound the wire agin and wrap the insulation with some electrical tape to keep it closed around the wire. Also, if you check the specific gravity of the battery acid in EACH and EVERY cell with a readily available battery hydrometer, you can tell the internal condition of the battery in a much more effective way then with a bench test of said battery. One bad cell reading , or even one marginal cell, means the battery needs replacement.

 

[nathan saunders]

Ok so cable is fine .I have codes now though. They are as follows p 0753, trans shift sol. P 1765 trans 12v relay .All relays and fuses are fine. So what now

 

[JR]

So what now

Post #7 above.

Focus on the charging aspect first.

 

[nathan saunders]

Every thing on the charging seems to be fine. Brand new batteries and alternator tests fine. Bench tests and voltmeter

 

[JR]

So what is the reading on the output of the altenator while the truck is running? This is very important to know, bench tests are ok to determine if the altenator itself is functioning properly but you also must determine whether or not the PCM is commanding the altenator to produce a charge as needed.

 

[nathan saunders]

13.4 to 13.8 is the reading on the alternator

 

[JR]

OK, so assuming all positives and grounds are clean and tight and your getting good voltage, the common denominator between Trans and charging system is the PCM. Being you had 2 unrelated systems begin malfunctioning at the same time there's a good chance this is where your problem is. It is mounted on the pass side firewall in the engine compartment. About the only thing you can do is check its connections, aside from that youre going to need to find a good live scanner to further (accurately) troubleshoot.

 

[nathan saunders]

Ok which means I'm fixing to throw down some cash haha. Well I really appreciate it

 

[JR]

If you know of someone with access to a live scanner (DRBIII or Snap on) you can diagnose further on your own. If not it is worth it to find a competent shop and pay the diagnostic fee. It's really the best (and often cheapest) way to pin down electrical anomalies like this

 

[nathan saunders]

So my truck has been in two different shops for a couple weeks now. The guy who has it now has replaced all transmission solinoids .Now wants to take my transmission apart because he thinks there is a valve stuck. But that makes no sense to me. How would the electrical part from volt gauge be related .