If anyone remembers my old post, I have done a bunch of stuff to it and just did a ton more this last month. Decided to make a new thread because the other one was getting old and enough has changed I think I need to start over.

 

So this began with me fighting what seemed like EMI in a particular spot in town. At the time with the Edge programmer, I could watch the boost signal drop to 0 then back up to the true value and back to 0 again, truck was fluctuating between tuned and not tuned is what it felt like. Then as I left the area the tuner would kick in again and it would pump smoke out and off it would go. No amount of throttle would change its behavior. It was weird.

 

One day my fuel pressure was 0. Found a melted wire for my air dog lift pump relay so I replaced the relay with another weather-resistant relay and taped it up and its been good ever since. So I'll get everyone caught up. Truck now has 208k miles. Transmission fluid is now valvoline ISO32 (napa p# 041) and has been for about a year. Rear diff has synthetic 75w140 plus additive.

 

Well the Edge died so I ripped it out and ran a super chips downloadable tune for a while and I actually believe the edge was responsible for picking up the interference as I haven't had any since I ripped it out, but other gremlins still haunt me.

 

Now, my problems are a really intermittent speedometer and also occasionally the transmission will flare up at about 40 mph and 3rd unlocked/locked. I did rebuild this myself, had to flush a ton of old fluid out and messing up the OD unit caused the OD piston and thrust bearing to bind and come apart which resulted in metal chunks everywhere and I believe to have cleaned hopefully all of that out and thats when I first replaced the sensor as well. Another important piece of the trucks history is that I sunk it in a giant mud pit 3 years ago, which is why the transmission went out and it also filled my rear axle with water which ive also flushed twice. The transfer case and front axle did not get water intrusion.

 

In the past here's what I did to address this. Changed transmission fluid enough times I got sick of buying ATF and got this 5gal iso32 for half the price and added a transmission additive. I have replaced the trans output sensor once and cleaned it later on. I have a feeling I need to replace it or clean it again because sometimes, only sometimes the speedometer fails to work. Or maybe the rear ABS sensor (truck has 2 wheel abs) but I have changed that sensor as well. Sometimes it comes back if I restart the truck. But it also came back on its own about 3 hours into a 6 hour drive last weekend. (edited to add) I have also changed the APPS. I think, I have an Oreilly unit on the truck right now. I don't actually remember. Ive changed it several times over the years between a calibrate it yourself one with the adapter plug and I have or had 2 factory ones I was swapping between back and forth.

 

Recently, the front main seal exploded. The actual dust seal part was missing completely, the seal part looked and felt abrasive, oil was everywhere. So I parked the truck for a bunch of work... Replaced front main seal, found that my killer dowel pin has been staked in already, extended breather hose down to a new catch can, replaced both oil cooler gaskets, replaced A/C suction line, new control arm bushings, shocks, sway bar end links. Cleaned radiator, fan, and shroud, extensively, also cleaned almost everything else. I stopped counting how much degreaser I used. Scraping grease and junk off with a screwdriver/scraper.. If I saw a ground connection I pulled it off and cleaned with brake cleaner. Removed the super chips tune and finally got a quadzilla. Amazing tune right out of the box. I discovered while changing the a/c line that I didn't fully remove the old noise isolator from the truck, it was disconnected from the harness but I left it dangling from the ground end so I finished that off. Of course gave it fresh rotella t4 15w40 oil and a factory oil filter.

 

I have spent a couple weeks searching about different forums and on here trying to come up with clues. So far, I found an old TSB about handheld radio interference; in the factory wiring diagrams I traced the speed signal to the 14 way ABS plug pins 8 and 12; and someone on a post here mentioned the bolted down junction block connector under the dash as a possible point of corrosion. I am actually looking at the 2000 trucks engine wiring map right now and am wondering why the dark blue alternator wire needs to go to the transmission relay or is that even a problem. I am going to inspect the transmission solenoid connector for any oil saturation or damage in general.. and I also have this sneaking suspicion that I may have a rear axle problem brewing but I haven't been under the back of the truck yet.

 

As for codes, the only codes ive seen in the last year was for the output speed sensor and the grid heater. I thought maybe the governor/transducer combo but those always give a code is what I thought unless im wrong about that. another wild thought.. years ago I thought the TC lockup switch was a good idea for me, is it possible I messed up and as a result the TCC driver in the PCM is intermittent?

 

unrelated.. I was also curious is there is a reason to have a "26v" in chalk under the oil cooler. I thought that was weird, im not aware of the truck having a junkyard engine so its gotta be factory for something

The rear speed sensor goes to the ABS box on pin 1 and on pin 8.  Connect a DVM to the pins and set to ohms function it should read less than 600 ohms but thats just a guess.

Set the meter to beep when the leads are touched together. Hopefully the sensor resistance is low enough to cause the beep to sound continuosly. Go under the truck and wiggle the wires at the rear end on the connector and all the way up into the main harness on the frame also try tapping on the sensor with something. If the beeper is interrupted at any time then there is a bad connection or broken internal wire from years of flexing. A new pigtale is probally available that is made of special flexible wire. Next move forward to the two connectors 

by the body mount and behind the drivers plastic inner fender and wiggle them and just open them up and spray cleaner in them. Test 2 connect the meter to pin 1and the other lead to a good ground. leave it set in the beep mode. It should NOT beep  Wiggle wires and harness along frame all the way to the ABS box if the meter beeps then a wire has been rubbed thru and is shorting to ground. The ABS box converts the bipolar sensor signal to unipolar signal that is output at pin 12 (VSS) that goes to the PCM. It then converts it to a CCD bus meeage

that goes to the cluster. A momentary hic-up in the bus causes the speed to quickly go out but the gauges can linger for a few seconds.

 

I'm not a fan of the cummins dry fit shaft seals that are supposed to perfectly wear to fit the crank.

     

I like these suggestions. I'll be having a car day at my friends house tomorrow I'll give this a go and report back what I find out

 

edit 1: fast forward to the next day now 1/1/24

 

He got sick overnight so im gonna have all day tomorrow to see what I can find. I did drive it over to his house and back. after approx 15 minutes of driving and at about 42mph it was hunting between 3 lock/unlock real bad and then further up the road now 20 minutes of driving at about 55mph it started jerking around a bit, just single jerks or maybe a few at a time but not the typical TC lock/unlock that I had years back. didn't see any anomalies on the gauges and the data log hasn't shown me any strange outliers yet. no codes of course. everyday it becomes more and more tempting to buy my own DRB scanner.

 

ill start with the abs connector tests here first and see what I can find tomorrow. depending what I find I think ill then review the AC voltage test and see if I can't find what my alternator is putting out with a borrowed fluke meter in a couple days

 

edit 2: 1/3/2024

 

on Monday 1/1 I went out and at least pulled apart the drivers side connector behind the wheel well. It was full of dirt so I sprayed it out 3 times with some electrical cleaner and let dry before putting together. I ran out of time so I didn’t get to test the abs wires but I confirmed my meter does have a beep function so I will get to it asap
 

Today, Wednesday 1/3, the alternator stopped charging, or rather the gauge displayed no charge voltage and said “check gages”. I shut the truck off to check the belt and alternator connector, which were both in place. When checked with a meter I saw 12.9v at the battery terminals so I restarted and saw 14.1 charging at idle. My meter is not a fluke so AC voltage testing isn’t possible until I get a chance to borrow a fluke meter. But for the next 30 minutes of messing with it and a short drive to get food and come back and this new voltage problem didn’t reoccur.

 

edit 3: 1/8/24

 

my backup car is suffering badly I need to give it attention before I have no cars. 99 Toyota Camry 2.2L with 280k miles on it. original struts are about ready to fall out of the mounts. its all rusted together. ill get back to the truck shortly.

 

bear with me as I attempt to stay on here and reliably take notes of everything I notice as I go along so I can finally figure this out.

I think I’ve found out a direction to go for this finally! And the speedometer hasn’t acted up since cleaning out that connector.

 

So. Last week I was sitting there and the quadzilla was running its warmup mode when suddenly, the engine returns to normal idle for a second then goes back. So I looked at my coolant temp on the QZ app and it was still around 95*, when it did it again! This time I was already watching and I saw it display a 0* reading at the same moment that it idled down before idling back up again.

 

So now, I’m staring at wiring diagrams related to the coolant temp sensor. Is there a known problem area for coolant temp sensor ground issues? A bad splice somewhere? Keep in mind this particular problem (referring to how it’ll intermittently act like the TCC lock/unlock but it’s not the same behavior) has been going on since before I did all that work to it last month. 

 

I think what’s happening is a very intermittent loss of coolant temp signal is causing the ECM to derate for a second before returning to normal.