Here it goes,
I have an idea, but let me lay down some facts for you first.
I'm wiring up my buddy's 1JZ using Aristo harness/ECU, and we've run into a sort of problem. Everything written below is what I've discovered doing my own research. Please, if any of it is incorrect, feel free to set me straight. I'm just trying to find a solution.
On the Toyota Aristo:
The Aristo ECU likes to have TWO speed signals to choose from. The primary would be from the No2 Speed Sensor (SP2) in the tail shaft, and the secondary (in the event that the primary signal is unusable or non-existent) would come from the No1 Speed Sensor (SP1). In the Aristo, in place of the mechanical speedometer port, is an electronic speed sensor. Namely, SP1. The Aristo did not use an ABS sensor in the tail shaft of the transmission, so it had SP2 as the primary sensor, and SP1 (in place of the mechanical port) as the secondary sensor.
On the Toyota 2.5L Supra (JZA70):
The 1JZ Supra ECU also like the two speed signals. However they are generated from different sources. The ECU still uses SP2 as primary and SP1 as backup. However, SP2 is generated from the ABS computer via input from the ABS sensor, and then transmitted to the ECU. SP1 is generated from the cluster via the speed cable. In the non-abs vehicles the ABS sensor is replaced with a generic speed sensor.
To Recap:
-Aristo SP1 = Speed sensor (4ppr) located at mechanical port
-Aristo SP2 = Speed sensor (4ppr) located at tailshaft (aristo trans only)
-JZA70 SP1 = Speed signal (4ppr) comes from dash thanks to speed cable
-JZA70 SP2 = (ABS) Speed signal (4ppr) comes from ABS ECU which is translated from ABS sensor on tailshaft (20ppr)
-JZA70 SP2 = (Non-ABS) Speed signal (4ppr) comes from non-abs speed sensor on tailshaft
The problem:
Most people around here limp their vehicles home when their speed cables break. This tells me that nobody has their PRIMARY speed sensor (SP2) connected, and the ECU is using the buffered signal from the dash as it's primary (supposed to be backup) source for the signal.
We do NOT want this problem. This is a dumb problem to have. We would like to provide the ECU with the correct signal to keep the transmission shifting even in the event the cable breaks.
So, if all of the information above is accurate (is it?), we could technically connect the SP2 signal of the ECU to the ABS ECU where it normally would output the speed signal to the 7M's ECT computer. Has anyone tried this? Am I way off in my assumptions? I have no scope to test pulses and whatnot, and all of the info on these sensors is just other users in other threads speculating. Hopefully someone will chime in with some confirmation.
In the image below you can see that B3-6 (Blue/Yellow) comes from the ABS computer and is input into the ECT computer as SP2. Would this be an acceptable signal to feed the Aristo ECU as a primary source for the speed signal?
Thanks for any help, sorry for the novel, I like to be precise!
PDF Referencing how the ECU uses these signals (Page 7):
http://www.autoshop101.com/forms/h16.pdf
I have an idea, but let me lay down some facts for you first.
I'm wiring up my buddy's 1JZ using Aristo harness/ECU, and we've run into a sort of problem. Everything written below is what I've discovered doing my own research. Please, if any of it is incorrect, feel free to set me straight. I'm just trying to find a solution.
On the Toyota Aristo:
The Aristo ECU likes to have TWO speed signals to choose from. The primary would be from the No2 Speed Sensor (SP2) in the tail shaft, and the secondary (in the event that the primary signal is unusable or non-existent) would come from the No1 Speed Sensor (SP1). In the Aristo, in place of the mechanical speedometer port, is an electronic speed sensor. Namely, SP1. The Aristo did not use an ABS sensor in the tail shaft of the transmission, so it had SP2 as the primary sensor, and SP1 (in place of the mechanical port) as the secondary sensor.
On the Toyota 2.5L Supra (JZA70):
The 1JZ Supra ECU also like the two speed signals. However they are generated from different sources. The ECU still uses SP2 as primary and SP1 as backup. However, SP2 is generated from the ABS computer via input from the ABS sensor, and then transmitted to the ECU. SP1 is generated from the cluster via the speed cable. In the non-abs vehicles the ABS sensor is replaced with a generic speed sensor.
To Recap:
-Aristo SP1 = Speed sensor (4ppr) located at mechanical port
-Aristo SP2 = Speed sensor (4ppr) located at tailshaft (aristo trans only)
-JZA70 SP1 = Speed signal (4ppr) comes from dash thanks to speed cable
-JZA70 SP2 = (ABS) Speed signal (4ppr) comes from ABS ECU which is translated from ABS sensor on tailshaft (20ppr)
-JZA70 SP2 = (Non-ABS) Speed signal (4ppr) comes from non-abs speed sensor on tailshaft
The problem:
Most people around here limp their vehicles home when their speed cables break. This tells me that nobody has their PRIMARY speed sensor (SP2) connected, and the ECU is using the buffered signal from the dash as it's primary (supposed to be backup) source for the signal.
We do NOT want this problem. This is a dumb problem to have. We would like to provide the ECU with the correct signal to keep the transmission shifting even in the event the cable breaks.
So, if all of the information above is accurate (is it?), we could technically connect the SP2 signal of the ECU to the ABS ECU where it normally would output the speed signal to the 7M's ECT computer. Has anyone tried this? Am I way off in my assumptions? I have no scope to test pulses and whatnot, and all of the info on these sensors is just other users in other threads speculating. Hopefully someone will chime in with some confirmation.
In the image below you can see that B3-6 (Blue/Yellow) comes from the ABS computer and is input into the ECT computer as SP2. Would this be an acceptable signal to feed the Aristo ECU as a primary source for the speed signal?
Thanks for any help, sorry for the novel, I like to be precise!
PDF Referencing how the ECU uses these signals (Page 7):
http://www.autoshop101.com/forms/h16.pdf
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