Sharing sensors between 2 ECM/PCM

[pokeytemplar]

I am trying to find out if it is possible to share sensors between two PCM's. I don't think there will be a problem with the Crank/Cam position sensors since all is required from the pcm is to see the rising or falling voltages. But what about the TPS or other sensors that use a reference voltage instead?

 

[WGJ]

I'm no electronics boffin you understand, but...I should have thought that 'sharing' sensors would require some sort of extra interface or buffer amplifier between the sensors and the ECU inputs to avoid electrical impedance mismatches/loading, etc. and also possible interference between the input circuitry of the ECUs.

Bill

 

[pokeytemplar]

Only one PCM would be used for the reference voltage since both use 5vdc as a reference. I do agree that having both of the PCM's monitoring the same line could introduce more impedance. If the change is low then it would not matter (engine is 180 but PCM's see 178) however if it is an extreme change then I would think a pull-up circuit could be used to correct the voltage offset.

I guess that is more of an electrical engineers expertise though....

 

[TurboXS]

It is possible to share most sensors. As discussed, in most cases you need one of the ECU/PCM to be a master and supply the reference voltages.

Awkward sensors are those where the ECM/PCM changes scales by changing the source impedance and some wideband O2 sensors.

 

[pokeytemplar]

Thanks TurboXS,

Plan on keeping the factory PCM including it's O2 sensors for the first stage of injection (as the master). Then use the second PCM to handle the second stage of injectors and PWM devices with wideband 02's. I guess the only thing to do is to try it and see what sensors are actually affected. Lots of logging will need to be done on this one!

 

[TurboXS]

In the past I have worked on Subaru, Nissan and Mitsubishi and piggybacked the following sensors;

TPS
MAF
MAP
Coolant
Air Temp
Crank
Cam
Knock
O2 (narrow and wideband)
plus a few more I can't recall at the moment.

Generally you should be fine.

By the way we did do a primary and secondary injector box a long time ago. We ran a double set of injectors of the same type. Under light load we would run one set. As the load increased we would run both sets and half (more or less) the pulse width.

 

[pokeytemplar]

Well that just about covers all of them. My plan is the same thing. Too difficult to try and get 120+lb injectors to act right idling through town. The factory PCM has all the part throttle stuff down perfectly and the aftermarket one is a dream when it comes to on boost fuel delivery. Let each do what they were designed to do. Once again thank you TurboXS.