Engine/Transmission (1994 - 1998) Check engine light

[BrandonThompson]

The check engine light has been coming on lately in my truck. I finally found out how to check the code and it is giving code 42 I believe. What does this code mean and how do I fix it. Doesnt seem to affect the way the truck runs. Also noticed the other night that my truck appears to be over charging. It normally has 14 volts when running according to the guage and to a volt meter. I rolled up the windows in the truck and when they got to the top the guage jumped to 18. I got home and thought it was just the guage so I put the volt meter on the truck and had my little brother push the swithes and it pushed 18 volts. What is going on with my truck?

 

[RHARVEY]

Sounds like the voltage regulator in your alt. is giving up the ghost!



Rick

 

[BrandonThompson]

Can you buy the voltage regulator seperate or am I going to have to buy a new alt.

 

[BrandonThompson]

I have been reading on here and it looks as though there is a regulator in the computer that controls charging. Is there one is the alt as well. How do I know which one is bad and why my truck is charging so many volts.

 

[crabman]

Brandon,

Code #42 is an open or shorted condition detected in the Auto Shutdown Relay circuit.

#1. Load check the batteries & clean terminals.

#2. Clean all batteries grounds to engine.

#3. If problem is still there then, remove alt. and have it bench checked. Warning: disconnet both batteries or you can blow the large fuse (120amp) in PDB.

#4. If alt. bench checks good, then it can be the Powertrain Control Module or something in the wiring between alt. & PCM.

crabman

You can get a Powertrain Diagnostic Procedures manual @ www.techauthority.com.

 

[BrandonThompson]

Last night I check the batteries and cleaned all connections. Had the alt tested and it is fine. What I found is that someone had bypassed the PCM with an old chrysler regulator. I hooked the wires back to the alt the way they were (the original harness) now it does not charge at all. The cruise also stopped working recently. The tach still works fine. Does this sound like the pcm. If so is it something I can change or should it go in somewhere. Or have it diagnosed somewhere? Checked the codes again and they are 42 and 46 (voltage to high). But that was with the aftermarket relay not the computer. I am growing old over this deal.

 

[crabman]

BT,

Looks like the previous owner jury rigged the problem he had with the charging system. Check out the thread in 911 section (Over Charging), follow the instructions and it will answer your question if the problem is the PCM.

C/C problem:

PCM is also used in the operation of the C/C, but do the following for peace of mind.

Check the servo & related hoses located under driver's side battery. It is easier to work on if you remove the d/s battery and batter tray. Battery acid eats up the hoses and servo unit.



Post your findings/fixes so we all can learn.

You can also find remaned PCM's but I do not have any info on where to find them. Maybe someone else can post the info.

crabman

 

[BrandonThompson]

Thanks for the info crabman. I will check tonight to make sure before I order one. They are 268 at napa for a reman. The dodge dealership said that they do not have to be reflashed, is that true? I will keep you posted.

 

[DEZLPWR]

How do you check codes on the 12v trucks? Do I need a scanner? If so, where can they be had for cheap?

 

[crabman]

BT,

No, it does not have to be flashed.



DEZLPWR,

The following procedure works for the 94-96 12V engines, for the 97-98 12V engines and ISB all require the DRB diagnostic tool to obtain trouble codes.



The codes can be displayed by cycling the ignition switch ON-OFF-ON-OFF-ON (leave in ON position, do not start engine) within 3 seconds. The CHECK ENGINE light will flash.

Example: A 34 code would be indicated by FLASH, FLASH, FLASH, PAUSE, FLASH, FLASH, FLASH, FLASH. Multiple codes may be displayed the same way. The display will end with a flashing number of 55.

If the problem is repaired or ceases to exist, the PCM cancels the code after 51 engine starts.



Do a search on google for DRB diagnostic tool. Be sure that it will read your vehicle before you buy.

crabman

 

[BrandonThompson]

Crabman,

Used your test last night and it appears that the computer is bad. Found a place that will rebuild it for 280 bucks and give a lifetime warranty. Thanks for the help.



Brandon

 

[crabman]

BT,

No problem!

crabman