Yeah that is right, I am in the “research” stage for retrofitting URPAS in my ’97 STS.
After about 2-3 hours of work I finally got a complete Ultrasonic Rear Parking Assist System from a 2000 DHS (fairly cheap $50).
This is the bench test (better said Persian carpet test ).
In case you don’t understand what is going on in the video, you are looking at the telltale assembly that normally mounts on the car headliner near the rear glass (central). You can also see 2 of the 4 ultrasonic sensors normally mounted in the rear bumper. As I am approaching to the sensors (normally the vehicle back up towards an object) the system pick up my position and illuminates the LED in the telltale assembly in the following pattern:
a) ~6 feet away first amber LED ON
b) ~3 feet away both amber LEDs ON
c) ~1 feet both amber LEDs and the red LEDs are ON
d) dangerously close all LEDs are flashing.
Here are the observations:
1) Works fine as long as the reverse signal is not grounded. In the car this input is pullet to battery voltage when shifting in reverse (by the reverse lights relay) and then pulled to GND when not in reverse trough the reverse light bulbs (the filament). So if you remove both reverse light bulbs your URPAS will work all the time. That is a caution for those of you with URPAS planning to update to LED for reverse lights.
2) It needs the RIM to operate otherwise it goes in error mode. Thank God for the diagnose mode (available by grounding the diagnose input) otherwise I had no clue why was not working. Basically the URPAS module monitors this output and expects to see it pulled to battery voltage by the RIM. Well I found a way around this issue by simulating the RIM input with a 10K resistor, so I tested with the RIM and w/o using the RIM simulate (the resistor).
3) Oddly, is not going in error mode if the VSS is missing (obviously I had none in my test), I guess is looking only for overspeed (>5MPH and ignores everything else).
4) Sound…that is the big issue here! It is not working as I would like it as in when the URPAS wants the chime it grounds the output. It actually does a frequency burst to communicate 1 chime, fast chime and I could not figure out how it requests continuous chime (I guess is higher frequency). I don’t have an oscilloscope so I was working with an LED, that is the most information I could get by observing the LED. But is enough for me to know that I am unable to use this chime output to connect a buzzer in case the RIM does not work fine on my databus. I would have to use the LED outputs in the following configuration:
a) 1 beep for the first amber LED
b) Slow beep for the second amber LEDs,
c) Continuous been for the red LED on
d) Fast beep with red LED flashing.
Unfortunately it will be an issue with the bulb test (every time shifts in reverse). Hopefully the RIM will work fine with my data line and post no code (as I am only connecting it for the chime request). Also the beeps will be there while in diagnose mode (actually that I can fix).
Let’s see how is the RIM behaving on my databus really, really hope it will be fine, otherwise it will be allot of extra work.
In this case is measure 10 times then 10 times more then cut.