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ALDL Description information for these platforms:
Chevrolet and Buick CLCC Full Function Systems
1984 - 1986
160 Baud ALDL operating characteristics:
Data Rate:      160 Baud                      Level:  Engine Lamp (12V)
Refresh Rate:   1.25 Seconds                    Modes: 20K, 10K, 500 Ohm
Stream size:    20 Bytes 
Byte Data Name Description
1 PROMIDA PROM Identifier (low word)
2 PROMIDB PROM Identifier (high word)
3 ADBAT Batery voltage in .1 volts
4 ADCOOL Coolant temperature sensor
5 FILTMPH Vehicle speed in MPH
6 ADPRESS  Pressure sensor in A/D counts:  (vac) APRESS = 2.711 * VAC(Kpa)+28.88 
(map)ADPRESS=2.711*MAP(Kpa)-38.66 
(2atmap) ADPRESS=2.711*MAP(Kpa)-10.24
7 OLDPA3  ESC counts  ESC counts = OLDPA3 + 16 Khz counts
8 ADTHROT  Throttle Position Sensor  %TPS = ADTHROT / 2.56
9 O2AAVG  Avereage of four oxygen A/D counts  O2 volts = O2AAVG * 230.4
10 DC  Duty cycle  %Duty Cycle = DC/2.56
11 M1 , MALFFLG1  Malfunction Flag word 1
12 M2 , MALFFLG2  Malfunction Flag word 2
13 M3 , MALFFLG3  Malfunction Flag word 3
14 CLCCMW  CLCC Mode word
15 MCU1IO  MCU input/output status word one
16 MCU2IO  MCU input/output status word two
17 EGRDC   EGR duty cycle (% duty cycle = EGRDC/2.56)
18 NTRPMX   Engine RPM (25 RPM per bit)
19 ADBARO   Barometric pressure in A/D counts   Pressure in KPA = (ADBARO + 38.86) / 2.711
20 ALDLCNTR  ALDL rich/lean change counter.  Value expressed is number of crossovers.
 
1984 4.1 Litre Chevrolet Truck ONLY
Byte Name Description
1-6   Same as 1984 Master Data Stream
7 ADO2A Oxygen sensor voltage  (voltage = ADO2A/230.3)
8-15   Same as 1984 Master Data Stream
16 MW2 Mode Word 2
17 DIAGMW3 Diagnostic Mode word 3
18  NTRPMX Engine RPM/25
19 SAP Total spark advance relative to TDC  (Advance in degrees = SAP*90/256)
20 LEVEL # This word contians the number 3
 
160 Baud Mode Words & Status Flag Descriptions
Byte Name BCD Description
MALFFLG1 MALF FLAG WORD 1 - 1985 & 1986
Bit     Code    Description 
0       24      Vehicle Speed Sensor 
1       23      Air Fuel Solenoid 
2       22      Nor Used 
3       21      Throttle Position Sensor 
4       15      Coolant sensor low temperature 
5       14      Coolant sensor high temperature 
6       13      Oxygen sensor 
7       12      No reference pulses (engine not running)
MALFFLG2 MALF FLAG WORD 2 - 1985 & 1986
Bit     Code    Description 
0       42      Bypass line error 
1       41      Tach input error 
3       35      Idle speed control nose switch shorted 
2       34      Pressure sensor 
4       33      Not used 
5       32      Barometric pressure sensor 
6       31      Not used 
7       25      Not used
MALFFLG3 MALF FLAG WORD 3 - 1985 & 1986
Bit     Code    Description 
0       55      Not Used 
1       54      Carb. mixture control solenoid 
2*      53      EGR failure on V8 
3       52      Not used 
4       51      PROM error 
5       45      Oxygen sensor rich 
6       44      Oxygen sensor lean 
7       43      Electronic spark control failure 
* (Not used in 1985)
CLCCMW CLCC Mode Word - 1985 & 1986
Bit     Description
0       Blended enrichment flag (1 = blended enrichment) 
1*      Purge 1 flag (1 = Purge 1 on) 
2*      Purge 2 flag (1 = Purge 2 on) 
3       Wide Open Throttle (1 = wide open) 
4       Wide Open Throttle Divert flag ( 1 = Divert) 
5       Rich/lean flag (1 = rich, 0 = lean) 
6       Non-Volatile memory bombed (1 = bombed) 
7       Closed loop flag (1 = closed loop, 0 = open loop) 
* - Not used in 1985
MCU1IO  MCU input/output status word one - 1985 & 1986
Bit     Description 
0+      Reference IRQ acknowledge (0 = interrupt) 
1+      Idle Speed control forward (1 = forward) 
2       A/C clutch or early fuel evaporation (V6 only) 
         (1 = solenoid comanded on) 
         Purge 2 (1986 V8 Only) 
3       Transmission lockup (1 = solenoid commanded on) 
4       Throttle Switch (1 = Switch closed) 
5       High gear switch (1 = fourth gear) 
6       Low/Mid gear switch (0 = third gear) 
7       Cruise engaged (1986 V6 only) 
         EGR Temperature switch (1986 V8 Only) 
         E cell input (0 = timed out) (1985) 
+ - Not used in 1986
MCU2IO MCU input/output status word two - 1985 & 1986
Bit     Description 
0       AIR Divert solenoid (1 = solenoid commanded on) 
1       AIR switch solenoid (1 = solenois commanded on) 
2       Not Used 
3       Throttle Kicker (1986) and (1985 Chevrolet) 
4       Not Used 
5       Park/neutral switch 
6       Air conditioner solenoid (0 = AC requested on) 
7       Air/Fuel solenoid (1 = M/C solenoid on)
M1 Malfunction flag word 1 - 1984
Bit     Code    Description 
0       24      Vehicle speed sensor 
1       23      Air/Fuel solenoid 
2       22      Not Used 
3       21      Throttle Position Sensor 
4       15      Coolant sensor low temperature 
5       14      Coolant sensor high temperature 
6       13      Open oxygen 
7       12      No reference pulses (engine not running)
M2 Malfunction flag word 2 - 1984
Bit     Code    Description 
0       42      EST Monitor 
1       41      TAC input error 
2       35*     ISC switch shorted 
3       34      Pressure sensor 
4       33      Not Used 
5       32*     Barometric Pressure Sensor 
6       31      Not Used 
7       25      Not Used 
* Not used for 1984 TRUCK engine
M3 Malfunction flag word 3 - 1984
Bit     Code    Description 
0       55      A/D converter (Truck Only) 
1       54      Carburator solenoid 
2       53*     EGR VAC. error  (Not used for 1984 Chevrolet TRUCK engine) 
3       52      Not used 
4       51      PROM error 
5       45      Oxygen sensor rich 
6       44      Oxygen sensor lean 
7       43*     ESC failure 
* Not used for 1984 Chevrolet TRUCK engine
CLCCMW CLCC Mode Word - 1984
Bit     Description 
0       Blended enrichment (1 = blended enrichment) 
1*      Closed loop since restart (1 = yes) 
2*      Idle mode (1 = yes) 
3       Wide open throttle (1 = WOT) 
4       WOT Divert flag (1 = divert) 
         Open loop level 2 expired (1 = yes) (Truck Only) 
5       Rich/Lean flag (1 = rich, 0 = lean) 
6       Nonvolatile memory bomb flag (1 = bombed) 
7       Closed loop flag (1 = closed loop) 
* 1984 Truck ONLY
MCU1IO MCU Input/Output status word one 1984 (Except Truck)
Bit     Description 
0       Reference Interrupt acknowledged (0 = interrupt) 
1       ISC Forward/Reverse (0 = forward) 
2       Early fuel evaporation (1 = solenoid commanded on) 
3       Transmission lockup (1 = solenoid commanded on) 
4       ISC throttle switch (1 = switch closed) 
5       High (fourth) gear switch (0 = fourth gear) 
6       Low/Mid gear switch (0 = third gear) 
7       E-cell input (0 = timed out)
MCU1IO 
(1984 Truck)
MCU Input/Output status word one for 1984 Truck
Bit     Description 
0       AIR control solenoid (1 = on) 
1       AIR switch solenoid (1 = on) 
2       EGR solenoid on (1 = on) 
3       Transmission lockup (1 = solenoid commanded on) 
4       Not Used 
5       E-cell timed out 
6       Low/Mid gear switch (0 = third gear) 
7       Air/Fuel solenoid test
MCU2IO 
MW2 (1984 Truck)
MCU Input/Output status word two 
MW2 - 1984 Truck
Bit     Description 
0       Air divert (1 = solenoid commanded on)   (except 1984 truck) 
1       Air switch(1 = solenoid commanded on)   (except 1984 truck) 
2       Not Used 
3       Cannister Purge (All exc. truck) 
         ALDL Mode (truck only) 
4       Diagnostic mode (truck only) 
5       Park/Neutral switch (1 = in park or neutral) 
6       Air conditioner solenoid (0 = AC requested on) 
7       Air/Fuel solenoid (1 = M/C solenoid on)
DIAGMW3 Mode Word 3 (1984 Truck Only)
Bit     Description 
0       Malfunction light on (1 = on) 
1       bulb flag 
2       Not Used 
3       Not Used 
4       Not Used 
5       Not Used 
6       Not Used 
7       Not Used

 
Description of mode operation
Mode Data stream Timers Special Functions
20K words 1-20 normal Normal Operation
10K  words 1-20 expired
Disable startup enrichment
Inhibit blended enrichment mode
Integrator reset criteria disabled
Burst knock retard disabled
Bypass RPM and temperature criteria for ESC enable.
ESC retard bit set
Inhibit cannister purge
Add calibrated amount of spark to calculation
3.9K words 1-20 expired backup spark and fuel control test mode
500 words 1-20 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 ( Check Engine Lamp)
  Pin G - Fuel Pump Prime
 
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