NEED HELP 05 Trailblazer Fuel Gauge Problem. Bad PCM?

TJBaker57

Member
Aug 16, 2015
2,897
Colorado
So if he has RPM, Voltage and Oil pressure then the serial bus from the BCM is working

His message states he does NOT have these gauges working.

However, he does have voltage and engine temp so he does have BCM and PCM serial data. I think the bigger concern is that the working gauges do not zero at ignition key to off.
 

JayArr

Member
Sep 24, 2018
504
Mission BC Canada
Thanks for the correction TJ, I mis-read that and thought those gauges were working.

I use a Hexacon iron, but they don't make these anymore but you can find NOS on eBay. It's a little higher quality than an American Beauty. Both are American made and last and last. There is no adjustment or control, it just plugs in and heats up but I can control the process with the tip I choose/make. It takes ordinary 3/16 copper slugs for tips so I buy the copper in 6 foot lengths and cut off approx 3" lengths and file the profile I want. It can be short and blunt for heavier joints or longer and filed to a thin point for finer work. Soldering isn't about the temperature of the iron, it's about the volume of heat transferred, too much and you damage the board, too little and it doesn't flow.

I also have a solder station, mine is an AOYUE 968. standard sort of rig with a small adjustable pencil iron and a adjustable heat nozzle. I only use the pencil iron from this one on very small jobs since it doesn't have much capacity and will get cold fast if asked to heat a large joint. It sits beside the microscope for changing very fine ICs.

Lastly I have a portable butane soldering pencil in the trailer for emergency repairs on the road. These can be expensive but they go on sale about twice a year around here. They are a little harder to control but they actually have lots of capacity so they are great for trailer repairs where you're trying to solder two 12 guage wires together. I can adjust the flame in mine so I was able to turn it down really low and change stepper motors in my cluster on a picnic table once. It also helped with a fan clutch wiring harness one time - a very handy tool.
 

mrrsm

Lifetime VIP Donor
Supporting Donor
Member
Oct 22, 2015
7,641
Tampa Bay Area
I'd like to get my hands on the "IPC Tester" being used on a GM IPC in this Video. Didn't know Dorman re-manned these:

 

Mramses

Member
Jul 19, 2020
322
17176352
Entonces, si tiene RPM, voltaje y presión de aceite, entonces el bus serial del BCM está funcionando, el bus serial del PCM está funcionando y la conexión directa para el RPM está funcionando.

En ese caso, cambiaría el Speedo por los motores paso a paso RPM.

y

Cambiaría la presión de aceite con los motores paso a paso del indicador de combustible.

Mine did that when they started to fail TJ. Remember there is no return spring in these, they must be commanded in both directions. The oil pressure would sometimes hang at about 1/4 point and when you restarted it would then zoom up to 3/4. At first if I restarted a bunch of times I may be able to get it to return to zero and read correctly but eventually the needle just went wherever it pleased. These are $2 motors so no one should be surprised that they don't last the life of the vehicle and no one should be surprised that the cluster from another vehicle or junk yard doesn't work right.

I guess I'm lucky that I can solder, I had no trouble swapping the motors around to do the troubleshooting and determine for sure that the stepper was the culprit. Others who don't solder well may be hesitant and look for alternative ways to troubleshoot and it will take longer and be more expensive.

Basically you need to KNOW that a cluster is working by putting it in a working vehicle. Don't trust something you've dragged home from a junk yard, that's not a solid troubleshooting approach because it introduces more unknowns and just further complicates things.
mine was good but trying to reprogram with tis2000 I stayed at 50% and stopped working well. I regret that but the damage has already been done. I bought one from another truck but it has this problem with the needles, the rest works well, the dash lights work, belt, emergency brake, gearbox position, turn signals, high beams, battery turns on and off well, check engine , service lights, anti-theft, ABS, everything works except the indicator needles
 

Mramses

Member
Jul 19, 2020
322
17176352
Good morning friends gmtnation I hope you all are well and are having a good samana. I was able to solve the problem of my cluster for now it works again and they return to zero when key is off. It works rpm, voltage, oil pressure, fuel still doubtful because I do not have much level but it is not observed that it rises even a little.
I replaced the engines of my old cluster that failed due to bad reprogramming and I installed it to the last cluster that I acquired from the junkcar. desolder them one by one (4 welds per motor) and replace in the cluster. Today in the morning the result is good for the moment. the difference between the motors is a code they have and the reason why I decided to change them to test if it worked was because they were too hard to turn and the others turn smoothly.
in advance thanks to all friends, have a good day
 

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