Problems with Yellowbox anyone

[My98RT10]

As described in another thread I installed my Yellobox last year after having done a gear change in 2017. Initially, everything worked fine but I now experienced a loss of speedometer signal after approx. 1h of driving. I checked connections which seem to be fine. After disconnecting and reconnecting the box it worked again. After another 10 minutes of driving signal was lost again. This time I disconnected the box and connected the jumper that came with the box. No issues for the rest of the drive. So I guess that the box has an issue...

When the signal was lost the speedometer was reading zero, of course. I also noticed a different behaviour of the car, e.g. deceleration pops were extrem in lower gears (not so much in higher gears like 4th or 5th). This makes sense as one of the input signals for engine management was wrong and not matching other signals. However, there was no CEL and also no code stored. I guess, the ECU is not able to recognize a faulty situation as the speedometer signal was still in the valid range (zero)?

Anyone else using the box? Anyone having had similar issues? Thanks for sharing your experience!

[dave6666]

I am aware of issues with the yellowbox. Tach and/or speedo. Which is the exact reason I never installed mine. I just leave the speedo wrong.

What version are you using? 4? 5?

[My98RT10]

I am aware of issues with the yellowbox. Tach and/or speedo. Which is the exact reason I never installed mine. I just leave the speedo wrong.

What version are you using? 4? 5?

I am not sure but maybe version 5? It is the one without dip switches and is actually black. It was sold by Unitrax together with the gears...

[Spitfire481]

I've had the V5 for about a year. Works great so far

[dave6666]

The black boxes I've had from Unitrax were not yellowboxes. They were for one, completely different looking, aside from yellowboxes being, well, yellow.

Post a pic of your box.

[My98RT10]

The black boxes I've had from Unitrax were not yellowboxes. They were for one, completely different looking, aside from yellowboxes being, well, yellow.

Post a pic of your box.

I posted pics in my initial thread... at least they claim to be yellow boxes on the ... well, ..box

https://driveviper.com/forums/threads/22548-Finally-installed-my-Yellow-Box-today?highlight=Yellowbox

[dave6666]

Mine is yellow. I guess black is the new yellow.

38749]

[My98RT10]

I checked the UNITRAX instructions coming with the box and the model name appears to be 2012VR. I also checked the Viper Student Workbook "Engine Management" with regards to the VSS (vehicle speed sensor) and there it says:

"The PCM requires the VSS to control the following programs:
- IAC motor (during deceleration)
- Injection pulse width (during deceleration)
- OBD II diagnostics (JTEC only)
- PCM mileage EEPROM
- Road speed shutdown
- Speedometer/Odometer

Note: Road speed shutdown is the PCM shutting of fuel injectors above a preset vehicle speed an rpm"

Seems to me like the road speed shutdown is not kicking in as PCM is reading a speed of zero, injecting too much fuel which cannot be burnt sufficiently, leading to this extrem deceleration popping when you step off the go pedal. I should say I really like the normal deceleration popping but in this situation it is way too much and does not sound healthy anymore... The car can still be driven ok as long as you avoid using the engine brake. If you put in neutral or press clutch while coasting no problems.

Well, that is at least my personal interpretation of what's going on. But I am very interested in other opinions, especially from those of you who have much more expertise on the Viper engine managment. So please post your theories here ;-)

[dave6666]

Have you thought about uninstalling it? At least for a test?

[My98RT10]

Have you thought about uninstalling it? At least for a test?

Yes, I uninstalled it by removing the box from the harness and connecting the supplied jumper. So, electrically it is now the OEM setup again (except for the additional harness which is still in place). This solved the problem so far. Maybe it is just me but I want my speedometer to show the correct speed (and not to count more miles than I am actually driving. ..)...

[LifeIsGood]

I never did a speedo recalibrator when I went to larger wheels/tires. I use a speedo app on my phone for accuracy. It's mounted next to the rear view mirror. My speedo is usually off around 3 at 50 mph, 4 at 75 mph and 5 at 100 mph. Good luck.