ws6transam.org - Dan's Performance Page

ALDL Description information for these platforms:
3.0 Litre Buick Port Fuel Injection System (1985 - 1986)
3.8 Litre Buick Port Fuel Injection System (1984 - 1986)
160 Baud ALDL operating characteristics:
Data Rate:      160 Baud                            Level:  TTL
Refresh Rate:   1.25 Seconds                    Modes: 20K, 10K, 3.9 K, 500 Ohm
Stream size:    20 Bytes in 1984 & 1985
                      25 Bytes in 1986
Byte Name Description
1 MW2 Mode Word 2
2 PROMIDA Prom Identifier (MSB)
3 PROMIDB PROM Identifier (LSB)
4 ISPMP IAC present motor position
5 COOLDEGA Coolant Temperature, A/D Counts
6 FILTMPH Vehicle speen in MPH
7 LV8 Filtered calculated load variable
8 NTRPMX Engine RPM (25 RPM/Bit)
9 ADTHROT Throttle position sensor (A/D Counts)
10 CORRCL Base pulse (fuel) closed loop operation
11 ADO2AF Oxygen sensor minor loop filtered value
12 MALFFLG1 Malfunction word 1
13 MALFFLG2 Malfunction word 2
14 MALFFLG3 Malfunction word 3
15 MWFA1 Mode Word (fuel/air)
16 AIRFLOW Unlimited mass air flow value
17 MCUINST MCU Status word
18 OLDPA3 Electronic spark control (knock) counter input
19 BLM Block Learn Multiplier, Base pulse fuel correction
20 ALDLCNTR Oxygen sensor transition counter
Remaining 1986 ALDL Byte descriptions for 10Kohm Mode
Byte Name Description
21 SAP+1 Spark Advance (with respect to TDC)
22 EGRDC EGR Duty cycle
23 ATPSCNT Air Temperature Sensor (A/D Counts)
24 BPW Base Pulse Width MSB
25 BPW+1 Base Pulse Width LSB
Remaining 1986 ALDL Byte descriptions for 20K, 3.9K, and 500 ohm Mode
Byte Name Description
21 NOCKRTD Degrees retard due to knock
22 ATPSCNT Air temperature sensor
23 ADBAT Battery voltage/ A.D Count
24 NOMALFCNT No malfunction count
25 EGRDC EGR duty cycle
 

 
 
Description of mode operation (20 & 25 byte systems)
Mode Data stream Timers Special Functions
20K words 1-20, 1-25 normal Normal Operation
10K words 1-20, 
1-25
expired
Bypasses lean clamp for integrator
IAC reset if RPM>2K for first time
Burst knock retard disabled
Add calibrated amt of spark to calibration
Inhibit cannister purge
Set idle to 1000 RPM
3.9K words 1-20, 
1-25
expired backup spark and fuel control test mode
500 words 1-20, 
1-25
expired
Diagnostic display mode
(check engine lamp flashes with O2 sensor)
 
ALDL Connector PINOUT
Pin A - Ground Pin B - Diagnostics Enable (Resistance w.r.t. A)
Pin F - T.C.C. Pin C - Air Switch Solenoid
  Pin D - Serial Data Line (TTL)
  Pin G - Fuel Pump Prime
 
NOTES:
The 1984 vehicles put eight bytes of information on the ALDL data stream when in normal (20K) mode. The words placed on the stream are:
1-  MW2
2-  Accumulated Fuel (3.91 msec usec. per bit)
3-  Accumulated Fuel (15.3 usec. per bit) LSB
4-  Distance  .0005 Miles per bit
5-  Vehicle speed in MPH
6-  Airflow (sec. / gram)
7-  RPM (25 / bit)
8-  Spark advance (90/256 degrees per bit)
ALDL Mode does the following:
Bypasses closed loop timers
Adds spark to spark calculation
Inhibits cannister purge
Controls engine idle speed to 1000 RPM
Inserts raw coolant count into COOLDEGA
Bypasses fast idle cam, EGR/PARK restriction, and burst knock routine
Engages ESC and toggles a bit when ESC is energized
Increments ALDLCNTR on every O2 sensor transition
Expires TCC timer
BCD Word descriptions - Discrete Data Information
Name Word Description
MW2 Minor Loop Mode Word 2 

Bit  Description 
0      Road speed pulse occurred (6.25 msec check) 
1      ESC Failure 
2      Reference pulse occurred 
3      Factory test (3.9 K ohm) mode 
4      Diagnostic (500 Ohm) mode 
5      ALDL (10K Ohm) mode 
6      High battery voltage - Disable MCU solenoid 
7      Air meter pulse occurred (6.25 msec check)

MWFA1 Fuel/Air Mode Word 1 

Bit  Description 
0  Clear flood flag (1 = cranked in clear flood mode) 
1  Learn Control enable flag (1 = enable store) (Tagged for unknown reason- drb)
2  Low Battery (Tagged for unknown reason- drb)
3  Proportional step taken flag (1 = rich, 0 = lean)
4  Highway fuel mode (1 = yes)(Tagged for unknown reason- drb)
5  First time closed loop flag
6  Rich/Lean flag
7  Closed loop flag (1 = closed loop)

MCUINST MCU Instruction Word 

Bit  Description 
0     Park/Neutral flag (1 = Park/neutral) 
1     In cruise or A/C head pressure not high enough 
3     Excessive power steering pressure(Tagged for unknown reason- drb)
4     Cruise control enabled(Tagged for unknown reason- drb)
5     Third Gear switch closed
6     Fourth Gear switch closed
7     A/C Requested

NONVRAM Non-Volatile Mode Word  [Cannot find where it fits in this structure - drb]

Bit  Description
0     O2 Sensor ready Flag (1 = ready)
1      Not Used
2      Not Used
3      Improper Shutdown flag (0 = proper, 1 = improper)
4      Not Used
5      Not Used
6      IAC Motor reset (1 = enable)
7      Malfunction 42 flag (EST Monitor)

MALFFLG1 Malfunction Flag 1 

Bit Code Description 
0    24      Vehicle Speed Sensor 
1    23      Air Temperature Sensor failed low (1984 models only) 
2    22      Throttle Position Sensor shorted 
3    21      Throttle Position Sensor open 
4    15      Coolant Temperature sensor failed low 
5    14      Coolant temperature sensor failed high 
6    13      Oxygen sensor failed 
7    12      No reference pulses

MALFFLG2 Malfunction Flag 2 

Bit Code Description 
0    42      Electronic spark timing monitor error 
1    41      CAM sensor fialure 
2    35      Not Used 
3    34      Mass airflow sensor failed low 
4    33      Mass airflow sensor failed high 
5    32      EGR failure 
6    31      Wastegate pulses not detected 
7    25      Air temperature sensor failed high

MALFFLG3 Malfunction Flag 3 

Bit Code Description 
0    55      ADU eror 
1    54      Not Used 
2    53      Water injection failure 
3    52      CAL pack missing 
4    51      PROM error 
5    45      Oxygen sensor failed rich 
6    44      Oxygen sensor failed lean 
7    43      ESC failure