Engine/Transmission (1998.5 - 2002) Low Voltage + No OD, 2 headaches or 1

[RShill]

My 2001 started suffering both low voltage readings and no overdrive at same time. Alternator tests fine out of the truck, not in it. I replaced both batteries(tested marginal). I'm told the voltage regulation is performed by the computer. Am I looking in the wrong direction? The OD is(?) electronicaly controlled, so could these be related. Oddly the truck runs and starts(driven seldom) fine except for the MPG with out OD.

 

[Missouri Mule]

How low is the voltage?

You Need to check out asd relay and battery temp sensor(under battery tray driver's side).

 

[RShill]

Bill, I'm an amateur mechanic but qualified electrician. What is "asd" relay?

 

[RShill]

Bill,

voltage on starting is 8to 10. At 50 mph its 0 to 4.

 

[Fishin Guide]

Doesn't the ECm have some conrtrol over the voltage?



Dave

 

[GarrettPetersen]

Have you checked the alternator fuse over in the power distrubition center

 

[Missouri Mule]

The ASD = Automatic Shut Down relay, it is in the power distribution center in the engine compartment. The asd supplies line voltage to the EVR (inside PCM/computer). EVR adjust alternator output(charging rate) from line voltage and temp reading from battery temp sensor.

Does your truck having any trouble cranking over? Your voltmeter mite be bad.

Are your grid heaters on when you start (pre and post)? They use a lot of juice. Need to use test light or mutli-meter to check to see if they are staying on. Doesn't really answer why your are running 0-4 vlots when at higher speeds. But the EVR mite have gone bad.

 

[Crash_AF]

Yes, the ECM controls both the voltage regulation and overdrive function as well as torque converter lockup and a host of other stuff.

I'd hazard a guess that you've either got wiring issues leading to the computer (rodent damage, etc) or the computer is dying.

If you turn the ignition on/off/on/off/on you should be able to get some diagnostic codes to read out on the odometer display. If you have some, post them here and we can decode them to try to point you in the right direction.

Later,
Joe

 

[RShill]

Moer symptoms

I got 4 codes off the odometer-1682,p-0753,p-1493,p-1765. I also drove it for a while and noticed a few things. The turbo doesn't apear to create much boost and when I let off the throttle I hear a pressure release infront of passenger. I can't find any thing wrong with the rubber boots to and from the intercooler. The truck did blow one of them off a few months ago going over a mnt. pass. I can't tell with the lack of turbo boost but I think the torque converter isn't locking up as well. I also looked for rodent damage unsuccessfuly.

 

[SnoKing]

P1682

Metering Oil Pump Malfunction

P0753

Shift Solenoid A Electrical/

1-2 Shift Solenoid Circuit Electrical

P1493

RCNT Solenoid Circuit Malfunction

P1765

Timing Solenoid Circuit Malfunction



http://www.troublecodes.net/OBD2/



Maybe this is a clue to 1493:

Also, the variable RCNT which represents the total number of reapply pulses ... a possible malfunction condition of the anti-lock system to the operator. ...



SNOKING



So looks like you might have a DTT transmission creating a couple of the codes. Mine creates 743, 753, and 1765.

 

[Crash_AF]

Hmm, my 99 FSM lists the following for those codes:

P0753 - Transmission 3-4 shift solenoid/Transmission Relay circuits
An open or shorted connection detected in the overdrive solenoid control circuit or transmission relay circuit in JTEC RE transmissions.

P1493 - Ambient/Batt Temp sensor volts too low
External temperature sensor input or Battery temperature sensor input voltage below acceptable range

P1682 - Charging system voltage too low
Battery voltage sense input below target charging voltage during engine
operation and no significant change in voltage detected during active test of generator output circuit.

P1765 - Trans 12 volt supply relay control circuit
An open or shorted condition is detected in the transmission relay control circuit. This relay supplies power to the TCC.

Replace your battery temperature sensor (common problem) and closely inspect the transmission harness for damage. If that's not the problem, then you need the transmission looked at.

BTW, according to the FSM, you should have the check engine light on for all of those codes. (It's been wrong about that before though... )

Later,
Joe

 

[Missouri Mule]

Crash_AF, 99 codes are listed on the 96 t0 2001 Generic OBDII Code defintions, these can be found in the 911 forum.



RShill check the wires going to battery temp sensor they can get corroded down under there and of course check the sensor.

 

[Crash_AF]

Crash_AF, 99 codes are listed on the 96 t0 2001 Generic OBDII Code defintions, these can be found in the 911 forum.

I was just passing along what my 1999 manual gave for those codes. Whether or not they changed after 99 (since my 1998 manual gives slightly different codes) I don't know. What I do know is that my list of codes makes more sense given his symptoms than the other codes given.

Later,
Joe

 

[Missouri Mule]

Crash_AF, Your definitions of the codes were right on. They matched the ones on the 911 forum.

 

[RShill]

ECM gone bad

Guys thanks for your help. With so many codes and symptoms all related to the ECM I had the dealership look at it. A week later and $800 poorer the truck runs great. thanks again for the insights.