Data link
Wade T. Braden
wbraden at ryker.itech.cup.edu
Tue Feb 25 22:16:57 GMT 1997
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I was able to get the data stream ( 160 Baud) using a hc11. This is
coming out of a 87' Firbird Formula 305 4 bbl. I haven't had time to figure
everythink comes out but I was able to get 20 bytes of info:
1-PROM ID
2-PROM ID
4-coolant temp
5-MPH
8-TPS
12-error code
13-error code
14-error code
18- RPM
Does anyone else have this from there car. I have 2 other lists, I
think one of them is from a 87-88 Fiero. I Attached them in a file.
snip------------------
TO GET THE ECM INTO DATA MODE A 10K RESISTOR IS PUT ACCROSS ALDL B & A
AND DATA ID READ FORM E
If you put a 20K accross pins A&B you get the data but it stays in
normal mode.
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i found this... its for an 87-88 fiero TBI 4-cyl: its NOT a p4 i dont
think, i think its a CCC system
Data rate is 160 baud, with a refresh rate of 1.25 seconds. The stream
length is 25 bytes. This stream should be accurate for MY 1985 and
1986.
Byte name Description
1 MW2 Mode word two
2 PROMA PROM ID MSB
3 PROMB PROM ID LSB
4 IAC IAC motor position
5 COOLAD Coolant temp in A/D counts
6 VEHSPEED Miles per hour (actual)
7 ADMAP Manifold absolute pressure
8 RPM Engine speed: (RPM)/25
9 TPSAD Throttle position sensor in A/D counts
10 INTFUEL Base pulse correction integrator for fuel
11 ADO2 Oxy sensor minor loop filtered value
12 MALFFLG1 Malfunction flag 1
13 MALFFLG2 Malfunction flag 2
14 MALFFLG3 Malfunction flag 3
15 MWAF1 Mode word 1 (air/fuel)
16 MCU1IO MCU I/O first status word
17 MCU2IO Microcontroller unit I/O status
18 BATAD Battery voltage in A/D counts
19 BLM Block learn multiplier (fuel correction)
20 ALDLCOUNT Oxygen sensor voltage transition counter
21 SAREF Spark advance (2.8944 degrees per bit)
22 EGRDC EGR duty cycle
23 MATAD Manifold air temperature in A/D counts
24 BPWMSB Base pulse width MSB (fuel injector?)
25 BPWLSB Base pulse width LSB
MW2 is a binary status byte that is bit mapped as such:
Bit Description
0 Road speed pulse occurred (6.25 msec check)
1 ESC active (1 = active)
2 Reference pulse occurred (6.25 msec check)
3 3.9Kohm resistor short @ ALDL link
4 ALDL pins A&B in diagnostic short (zero ohms)
5 ALDL pins A & B in ALDL mode (10 Kohm resistor)
6 High battery voltage: disable MCU solenoid discrete ckts
7 Old Air/fuel data flag
Mode word 1 (air/fuel) is bit mapped as such:
Bit Description
0 Low RPM hysteresis
1 Learn control enable (1 = store)
2 Low battery IAC inhibit
3 I don't have any idea
4 ASYNC pulse
5 1st time closed loop flag
6 Rich/Lean flag (1 = rich, 0 = lean)
7 Closed loop flag (1 = closed)
MCU first status word is bit mapped as such:
bit description
0 IAC coil A
1 IAC coil B
2 IAC coil on/off (1 = on)
3 I have no idea
4 Vacuum switch active (1 = active)
5 A/C (0 = A/C enabled)
6 Wastegate bypass control (1 = bypass - Cool eh?)
7 Park/Neutral switch (1 = In park or neutral)
MCU second status word is mapped as such:
0 A/C clutch engage
1 Coolant pullup resistor (0 = 4Kohm, 1 = 348 ohm)
2 Transmission converter clutch engaged
3 Again, no idea.
4 No idea.
5 Power steering activity
6 I don't know
7 I don't know
; The data frame consists of a start pattern of 9 ones, (the frame
; sync pattern) followed by the actual data. Each data word is
; 9 bits, but the first bit is always a 0. Thus, the leading bit is
; stripped away, leaving the 8-bit data byte. MSB is transmitted first.
; The total frame length is 19 data bytes (?).
;
; The following is a list of the bytes in order of reception:
; Note-- the address is controlled by table @ 0d4c5h for type 4E ECU
; an interesting aside--can change RAM/ROM location that is
; monitored by altering address in EPROM table
;
; A/D conversion values based on 256 counts = 5.000 volts(not 255 counts!)
; Thus, 1 bit = 19.53 mv.
;
; ID_HIGH high byte of eprom ID#, location 0d002h
; ID_LOW low byte of eprom ID#, location 0d003h
; IAC current idle air count
; COOLENT coolent temp, deg C= (0.75 x value) - 40
; MPH miles per hour
; MAP manifold air pressure KPA = (0.3125 x value) + 20
; RPM RPM = 25 x value
; TPS throttle position, % = (100 x value) / 255
; INT integrator value
; O2 o2 sensor value, mv = 4.50 x value
; ERR1 error codes byte 1
; ERR2 error codes byte 2
; ERR3 error codes byte 3
; AFSTAT air/fuel status byte
; BATT battery voltage, Volts = value x 0.195
; IOSTAT descrete IO status byte
; KNOCK knock counter (rolls over)
; BLM block learn mode value
; ALDL aldl counter (rolling--frame cntr?)
;
; Use 2 EPA channels to perform the serial input function.
; EPA0 is set-up to detect a falling edge on PORT 1.0, then
; EPA1 is used to sample the bit value in the middle of the
; the BAUD period.
;
; 6.250 mS (=1/160 baud)
; |<------------------------------->|
; | |
;
;---------+ +\\\\\\\\\\\\\\\\\\\\+------+ +\\\\\\
; | | data here (1 or 0) | | | next data bit
; +-----+\\\\\\\\\\\\\\\\\\\\+ +-----+\\\\\\
;
; | | | |<--->|<---1.65 mS high always
; | | |
; | | |
; | | +--sample bit here, t=2.400 ms
; |<--->| from falling edge bit start
; |
; +--200 uS start time (low always)
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Wade T. Braden Email: wbraden at ryker.itech.cup.edu
408 Burton Ave. Web: http://www.itech.cup.edu/~wbraden/
Washington, PA 15301 Major: Electrical Engineering Tecnology
(412)222-8964 at California University of PA
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