Not strictly tuning topic, but I think might be interesting.
I'm installing 1998 V6 F-body ABS system (3channel Bosch 5.3) into my 3rd gen Firebird. The ABS sensors part is not so complicated and I have most of the issues resoled (at least on the paper). Just for future reference: 4gen front reluctors have 47 teeth, rear diff carrier reluctior has 106 teeth.
It gets tricky when I got to the Traction Control part. The donor car had 3.8 engine and had the traction control option. I'd like to have it working as some kind of launch control assistance to reduce timing or fuel (without ETC).
My car has 357 SBC with Vortec heads and 2" TBI + 4L60E controlled by $0D PCM.
From what I have found from ABS service manuals and wiring diagrams, there are three signals used between EBTCM and PCM for T/C:
- Tach signal from PCM ( not much information on this, but it is quite self explanatory ),
- Requested torque (from EBTCM to PCM),
- Delivered torque (from PCM to EBTCM),
The ABS service manual states that the requested torque signal is pulled up by PCM to 5V , and is 128Hz PWM signals, with valid range of 5%-95%. (Permanent hi or lo condition is a fault). There is no information about the return Delivered torque signal pull up voltage or frequency, but I'd guess it should be the same.
EBCM and PCM simultaneously control traction control. EBCM
sends a requested torque message via a Pulse Width Modulated (PWM)
signal to PCM. Duty cycle of signal is used to determine how much
engine torque EBCM is requesting PCM to deliver. Normal values are 10-
90 percent duty cycle. Signal should be at 90 percent when traction
control is not active and at lower values during traction control
activations. PCM supplies pull up voltage that EBCM switches to ground
to create signal.
If a defective requested torque signal is detected by PCM, a
message is broadcasted back to EBCM via class 2 data line. DTC sets
anytime ignition voltage is present and PCM detects requested torque
PWM signal is less than 5 percent duty cycle or greater than 95
percent duty cycle or requested torque PWM signal is not present for
PCM sends a delivered torque message via a Pulse Width Modulated
(PWM) signal to EBCM confirming delivered torque level for proper
traction control system operation. EBCM supplies pull up voltage.
From what I understand the service manual, the normal state is both signals at 90% PWM. When the EBTCM wants PCM to reduce power, it lowers the requested PWM duty cycle appriopriately, with minimal duty cycle of 10%.
The PCM retards timing and sends back confirmation to EBTCM by lowering Delivered PWM duty cycle, also with minimal duty cycle of 10%.
What I don't know is how the PCM actually performs the spark reduction and what is the relation between Requested PWM, actual spark retard and delivered PWM.
Has anyone investigated this part of the code in 0411 and simmilar PCMs? I guess the T/C code should be the same in every PCM using this Bosch 5.3 EBTCM.
There is a section for Traction Control related tables and parameters in EFI live definition, but it's hard to tell what exactly those tables do. There is also a lot of probably unnecesary (for my needs) torque management stuff connected.
Maybe we could come up with a way to write a routine for 427 ECM for T/C, with unused PWM pins to communicate with EBTCM.
There is another question whether some additional data is sent by class 2 OBD network, but I'll have to later figure out that transmission anyway to light ABS telltales on the dash.
Thanks for any of your input. I'll try to post my findings here as I progress :)