NEED HELP 05 Trailblazer Fuel Gauge Problem. Bad PCM?

[TJBaker57]

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.

 

[TJBaker57]

guess I'm lucky that I can solder, I

As an aside, which tool would you use to reflow solder joints? I have several pencil types plus a chinese made reworking station with both air and pencil types with adjustable temp settings?

 

[JayArr]

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]

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]

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]

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

 

[dstairs]

Aha!!!

Since this was posted I had the opportunity to do more research and if I'm right in 2004 they dropped the 1155 PID and instead implemented the equivalent SAE standard PID which is 002F. They kept this in 2005 but then in 2006 went back to the 1155 for that year but then in 2007 changed back again to match the 2005!!

So if you still have that PID definition in Torque Pro go in there and change the "1155" to "002F" and let's see what that gets us.

Would this work for a 2006 trailblazer LS 4.2L?

 

[TJBaker57]

Would this work for a 2006 trailblazer LS 4.2L?

Are you asking about PIDs 1155 and/or 002F ??

I have a 2006 PCM and at least on that unit both fuel level PIDs 1155 and 002F are supported.

It is important to note that they report different data in that the 002F reports the fuel level directly and 1155 reports the fuel level sensor voltage. And for this particular case the voltage is highest when the tank is empty and the voltage drops as fuel level increases.

 

[dstairs]

Are you asking about PIDs 1155 and/or 002F ??

I have a 2006 PCM and at least on that unit both fuel level PIDs 1155 and 002F are supported.

It is important to note that they report different data in that the 002F reports the fuel level directly and 1155 reports the fuel level sensor voltage. And for this particular case the voltage is highest when the tank is empty and the voltage drops as fuel level increases.

Yes I was talking about them and thank you. I just bought an 06 and the guages are all wonky. Only rpm and speedometer work correctly. The pic is of the instrument cluster when I turned it off last night.

 

[azswiss]

Looks like someone has already opened the IPC up & fiddled with the needles (esp. fuel & oil pressure). When disassembling the IPC you need to remove the needles in order to remove the face plate; when reassembling (e.g. after replacing bulbs or steppers) you need to make sure that the needles are properly aligned with their power-off locations; this is clearly not the case with fuel level & oil pressure. Voltage & temp appear to be a little off as well.

Do the incorrect gauge needles move or are they completely dead?

 

[TJBaker57]

That may be stepper motor failure? I cannot say for sure as I have never personally seen stepper motor failure. When the key is first turned to RUN do the gauges all sweep counterclockwise towards zero??