Speedometer?

[Brav302]

Is there a place in the tech 2 to see the speed the PCM is sending to the speedometer? Mine is off quite a bit. I’ve verified the tire size is correct; couldn’t find where I could verify the gear ratio though. Thanks

 

[JOHNGAAA1]

GLOVE BOX TAG

 

[Rocket Surgeon]

Cannot speak for a tech 2, but...

I have a cheap OTC scanner that can do live data. It shows what the computer sees as speed.

My green 98 k2500 is about 10 mph slower than what the cluster reads... and actual speed is in between those values.

GFs HHR speedo is 1 mph faster than the computer sees

1996 regal, parents car had NOTHING synced. Evidence of cluster tampering. "low mileage" car that was a rebuilt wreck that had a clean title. Synced every needle with the OTC scanner while test driving. RPM, temp and speedo were off. Ran out of gas with 1/2 tank indicated,


I also did an injector swap and verified the best replacement injector with nothing more than short term and long term fuel trim data from the same scanner. 30k miles of testing and WORKS AWESOME. Ask if you have an 06-07 HHR.


Don't forget to compare speed to more than one GPS app.

 

[GoToGuy]

Is there a place in the tech 2 to see the speed the PCM is sending to the speedometer? Mine is off quite a bit. I’ve verified the tire size is correct; couldn’t find where I could verify the gear ratio though. Thanks

The tag on driver's door jam edge or body side has OE installed size/ rating tires. Also the glove box door RPO tag has three digit code for installed tire size. Same tag has gear codes, and all options your truck was built with.
Get service manual for your year, download here on the forum free. In the first section of manual just after VIN definition, has all RPO codes built that year, defines all options so you can see exactly what your truck has, or what was built with. Good luck.

 

[Brav302]

Thanks for the input. I guess my questions weren’t very clear. I know what the truck is supposed to have for tire size, and gearing. I’d like to know where using a tech 2 scan tool I can verify what gearing it is programmed for. I’d also like to see the live speed from the PCM, so I can see if the speedometer is displaying what is being sent, or if the issue is in the speedometer itself.

I found and verified that the correct tire size is programmed. Thanks

 

[Brav302]

Had some time to play with this today and was able to find it. Below are the screens to cycle through:

F0 Diagnostics
Select year
Select vehicle type
F0 Powertrain
Select engine
Select product line
Select transmission
F1 Data Display
F1 Transmission Data Display
F0 Transmission Data
Vehicle speed is on line 8

From the PCM my speed is spot on, so just need to figure out the deal with the speedometer.

 

[Supercharged111]

Had some time to play with this today and was able to find it. Below are the screens to cycle through:

F0 Diagnostics
Select year
Select vehicle type
F0 Powertrain
Select engine
Select product line
Select transmission
F1 Data Display
F1 Transmission Data Display
F0 Transmission Data
Vehicle speed is on line 8

From the PCM my speed is spot on, so just need to figure out the deal with the speedometer.

Gonna need to tune that to correct the speedo if it's a Vortec truck.

 

[Schurkey]

WHAT VEHICLE???

In '88, for example, the computer doesn't "send" a signal to the speedometer. The instrument cluster sends the vehicle speed to the computer. The cluster is responsible for "decoding" the VSS signal, and distributing it to the speedo, odometer, cruise control module, ABS module, and the main computer.

 

[Brav302]

2000 K3500, 7.4, Automatic.