Need help - 98 electrical problems and 4L60E transmission codes

[Megibbs27]

Hello everyone. We have a 1998 1500 5.7L 4L60E 2WD truck that we've had for about 10 years. In 2018, we put a remanufactured 4L60E (ordered from the dealer) in the the truck and then we ended up getting a new truck so we parked the 98 and hadn't touched it until now. So the transmission only had about 50 miles on it when it was parked. Last summer, my husband changed out the entire dash while it was sitting. While he was putting the new dash in, he removed the aftermarket alarm that was hooked up to the wires.

A few months ago we finally decided to get it back on the road so we swapped all the fluids and filters out and started it up. The truck drives amazing and just as good as it did before it sat for 3 years. Except it has been having electrical problems and engine codes since we got it running. These were issues that were not present before the truck sat for 3 years. I've been reading a few different forums and I'm not sure if its an electrical problem causing all of this since the dash was replaced or if being caused by the ignition switch or a bad ground, etc. Anyway, hopefully I can get some help from yall.

Here's a list of what's currently going on:

*First it had P1860 and P0420 - my husband replaced the TCC solenoid and switch, put in a new transmission filter, replaced the 2 front 02 sensors. We drove it around for a few days and checked the codes again and now it has more: P1860, P0420, P0740, P0134, P0154
*The headlight switch is hot to touch. We ordered a new one and it still gets hot so we have kept it unplugged
*We've checked the fuses and didn't find any that were blown and they are all working
*The left blinker flashes lights on both sides (like hazards) however when you hit the brake with the left blinker on, then the left blinker works properly. If you let off of the brake, it goes to flashing hazards again
*The right blinker works normally with the headlights off
*If the headlights are on, neither blinker works and it makes a buzzing noise
*horn doesn't work
*clock spring is loose
*gas gauge is inaccurate and moves from F to E back and forth whenever it pleases
*speedometer is off and it's at different increments at different speeds (we do have 35's on the truck but this is a new issue)
*AC blend door motor goes in and out. If the AC doesn't blow through the vents then we tap the blend motor a bit and then it will work


We mainly want to get the electrical problems and the codes taken care of now so we can drive it without worrying. The speedometer, horn, AC motor etc. are things we don't care to fix right away, I just listed all the symptoms I can think of incase they are related.


Has anyone had any similar problems? I read that having P1860 with P0740 then it could be a bad ignition switch. The truck starts up fine and doesn't have any issues turning on or driving. Surprisingly it drives really nice and smooth. I also read it could be the multi function switch causing the blinker problems. The truck has dual exhaust and had high flow cats put on around 2014. So I'm not sure why it had 02 sensor codes first and then we replaced the sensors and now its showing 02 sensors again along with cat codes. We took the truck to a mechanic last week and he basically gave it back to us and said take the dash apart and check for kinked or exposed wires. Maybe it has something to do with the alarm my husband removed? Does anyone have a wiring diagram where we can find the grounds?


We've had this truck since 2011 and have taken it apart and put back together many times over the last decade and I've been pretty good at solving all of our problems in the past by reading forums but I am officially stumped this time around.

Any info is greatly appreciated! Thank you!!

 

[thegawd]

A bad ignition switch has the following symptoms:

-No Speedo at all
-No gear indicator light that shows what gear you have selected.
-3rd gear only and it will not shift at all. you can manuall shift through 1st or 2nd to start moving and then put it in 3rd or drive dosent.matter really because it's only 3rd.
-A lot of transmission codes, like 6-7.


the same symptoms can be achieved by pulling the prndl fuse in the end of the dash or by removing the big round transmission plug. this is called "Limp Mode."

one way to test the ignition switch is to check the voltage of the prndl fuse in the end of the dash. it should read the exact same voltage as the battery. if it's different at all and gives you a different voltage everytime you turn the key then you indeed have a faulty ignition switch.

if this fuse checks out them you need to do the exact same test but on the big round plug at the transmission on Pin E. Pin E is the only 12v positive feed for the transmission and it comes from the PRNDL fuse that you checked first. find a drill bit that fits perfectly in the plug for testing. also use that drill bit to clean out all the contacts in the plug along with some electrical contact cleaner.

with only 2 transmission codes you may have a wiring problem or bad solenoids inside the tranny.

is there any chance this transmission is under warranty? that would be nice if it was and you could have them test it. hell most reputable transmission shops will diagnose for free and be honest with you BUT you need to find that shop first....

good luck.

Al