Fiero ECM codes for 1985 and 1986 6 cylinder applications

[Daniel Burk]

Here's the 2.8 litre Pontiac TBI injection system data stream.

I don't have the Fiero mailing list, but someone here can forward it
I am sure.

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

That's about all I know.

	-- Dan.