Auto high beams

[daveprice7]

Why is it again that a car part that is basically a screen and a couple analog gauges is the part that stores any vehicle information, at all? Shouldn't the odometer value just be stored in a black box somewhere so the gauges can be dumb? This must be some backwards regulation carried over from 1950.

Sponsored

 

[jeepoch]

Why is it again that a car part that is basically a screen and a couple analog gauges is the part that stores any vehicle information, at all? Shouldn't the odometer value just be stored in a black box somewhere so the gauges can be dumb? This must be some backwards regulation carried over from 1950.

Yep. There are some manufactures that have gone that route using dumb displays. FCA for the Wranglers, maybe due to historical legacy reasons, look very much like they continue using clusters that persistently store the Odometer value.

This does have some advantages however. It's much harder to tamper with the true odometer reading with more locations (devices) that store duplicate values. Whenever any number of these values disagree, the probability of tampering goes way up.

However some care must then be made that all copies are updated near simultaneously (dependent on the distance scale) such that all copies always reflect the same value. For tenths of a mile this would be trivial. For meters or feet this would be difficult at highway speeds.

Dumb clusters while easier to maintain, eliminates a device that can store such an important vehicle metric. I'm also sure that there are likely federal or state laws that require that the odometer value must be maintained on more than one device. The manufacturers likely require even more in case of device failures. That way two or more devices still hold the true odo value just in case one (or more) of the devices like the cluster fails. The engine, transmission and body controllers still all maintain their own copy.

Some vehicles however do not have trans or body computers. So traditionally the engine and cluster are the only two natural devices available. Many car companies, including FCA who likely share components between vehicle makes, likely tend to keep this design to give them the most options in any type of future deployment.

Jay

 

[daveprice7]

Yep. There are some manufactures that have gone that route using dumb displays. FCA for the Wranglers, maybe due to historical legacy reasons, look very much like they continue using clusters that persistently store the Odometer value.

This does have some advantages however. It's much harder to tamper with the true odometer reading with more locations (devices) that store duplicate values. Whenever any number of these values disagree, the probability of tampering goes way up.

However some care must then be made that all copies are updated near simultaneously (dependent on the distance scale) such that all copies always reflect the same value. For tenths of a mile this would be trivial. For meters or feet this would be difficult at highway speeds.

Dumb clusters while easier to maintain, eliminates a device that can store such an important vehicle metric. I'm also sure that there are likely federal or state laws that require that the odometer value must be maintained on more than one device. The manufacturers likely require even more in case of device failures. That way two or more devices still hold the true odo value just in case one (or more) of the devices like the cluster fails. The engine, transmission and body controllers still all maintain their own copy.

Some vehicles however do not have trans or body computers. So traditionally the engine and cluster are the only two natural devices available. Many car companies, including FCA who likely share components between vehicle makes, likely tend to keep this design to give them the most options in any type of future deployment.

Jay

I don't have an issue with vehicle data being stored in several "black boxes" throughout a vehicle. Integrating it into an LCD screen? That's just silly. How difficult would it really have been to put a few screws on the gauge cluster and give the LCD screen a part number? Hey, you got a good deal on your Jeep because of it, but.. what a pain. Now I'm gonna stress about if/when that stupid LCD screen fails.

 

[jeepoch]

I don't have an issue with vehicle data being stored in several "black boxes" throughout a vehicle. Integrating it into an LCD screen? That's just silly. How difficult would it really have been to put a few screws on the gauge cluster and give the LCD screen a part number? Hey, you got a good deal on your Jeep because of it, but.. what a pain. Now I'm gonna stress about if/when that stupid LCD screen fails.

Dave,

I concur with your point. They can locate little storage units all over the place. The intelligent battery monitor, hvac panel, practically anything connecting to the CAN Bus. It doesn't necessarily have to be the instrument cluster.

I'll raise your question to one deeper level. Why does the cluster care one way or the other whether you have an auto dimming high beam? I don't believe there is any special lamp for the auto high beams. They are either bright or dim independent of how they got that way. So why is the cluster involved with the automated functionality of the high beam circuit at all?

My guess is that little Odometer memory storage device is also being used for other vehicle package configuration data. I'll bet that if FCA was capable of managing the reprogramming of the cluster in the field, the personality of this cluster indicating the presence of a safety package being installed (falsely) could be reprogrammed in place at the dealership without affecting the odometer reading in the slightest.

However, their paranoia of (even inadvertantly) providing a tool or mechanism that could potentially roll back the mileage (whether or not an underlying fault code is set due to mismatch) is likely keeping the cluster as a non-serviceable unit in the field. Any and all reprogramming must only be done by an authorized agent with a pair of them specifically. The old one being replaced with the reference mileage (to then be zeroed) and the new one with the copied value to be reinserted. No exceptions.

Jay

Sponsored