This is designed to simulate VT-VY PCM data. The ALDL simulator already includes a mode to do that, but the data it can include is limited (basically only does warning lights).
- PCM_sim_prototype.png (490.78 KiB) Viewed 7368 times
Think of it as a PIM (powertrain interface module), except instead of translating data from another network (CAN / VPW), it translates from discrete physical inputs/outputs.
This came about after someone requested something to do this. They have a VY and have replaced the PCM with a haltech, but want to keep the rest of the vehicle like factory.
This module (so far) does:
- VATS output (if you want to somehow prevent the car running if a valid key isn't inserted)
- MIL, OIL, power lamps
- Low speed fan request input (to send to BCM)
- AC Request output (to retain factory AC dash switch)
- Coolant temperature input
- Gear / selector position input
The big one that was requested is the coolant input. The factory cluster gets coolant temperature over ALDL, so without it you would need to use an aftermarket temperature gauge.
This module can basically read a 0-5v signal and has a lookup table to convert that to temperature. It has a built in 330 ohm pullup resistor, or the option for a custom pullup resistor you can solder in yourself, and it can switch between the 2 depending on how its configured. It also has 2 options for lookup table, the default/standard one which is designed to work with the 330 ohm resistor and an LS1 style coolant sensor (and from what I can tell, probably many other GM fluid temperature sensors), or a custom table you can configure over ALDL. In effect there's 3 ways you can use it:
- Wire an LS1 sensor to it and send it.
- Use some other sensor, with an appropriate pullup resistor, and configure the voltage/temperature relationship into the custom lookup table.
- Piggyback off an existing sensor (by not fitting a pullup), and configure the voltage/temperature relationship into the custom lookup table.
- PCM_sim_prototype2.png (538.07 KiB) Viewed 7368 times
The gear /selector position input can also work in a couple of different ways:
1. Connect directly the the PRND A/B/C/P wires of the range switch, in parallel with the PCM or auto trans controller.
2. Use an analog 0-5v voltage (eg. from a pot mounted on the shifter somehow). You can configure custom voltage ranges (min / max values) for each gear.
The other big thing which isn't added yet is fuel usage. Not entirely sure which way to go about that yet. The ALDL data has 2 separate values, fuel used (sum of all fuel used this ignition cycle) and fuel flow (eg. instantaneous fuel usage). I need to determine how the cluster actually uses these to calculate l/100km etc. exactly. If it's using the vehicle speed data which also comes over ALDL, then I will need to add a speed input to the simulator as well. If it uses vehicle speed from the actual speed input to cluster, then probably not.
The idea is to have it so it can be connected to an injector, and will measure injector pulse widths. The flow rate / dead time will be programable like the other items so it can be dialed in. Then it can watch the injector to calculate and send fuel used/fuel flow data to the cluster. That's what I'm thinking at the moment anyway.
I've currently only got a couple of prototypes. I've sent one off to be tested in the real world this week.
Before I order any more PCB's or make any more changes, I thought I would post it up here.
If anyone has any ideas / requests / suggestions I would love to hear them now (before I order 50 of them and then work out I need a hardware change to implement a new feature)
I've attached the instructions PDF for more details.
For the configuration over ALDL: Ideally I would like to have a lightweight windows application that could work with an ALDL serial cable or J2534 device. Instead of having to manually send commands with something like the OSE flash tool. But that's a whole other project of its own (eg. when I get spare time and want to dip my feet into that kind of thing)
