Chevrolet MFI ALDL Description Information

ALDL Description information for these platforms:
2.8 Litre Chevrolet Multiport Fuel Injection System (1985 - 1986)
5.0 Litre Chevrolet Multiport Fuel Injection System (1985 - 1986)
5.7 Litre Chevrolet Multiport Fuel Injection System (1985 - 1986)

160 Baud ALDL operating characteristics:

Data Rate:      160 Baud (All)                     Level: TTL
Refresh Rate:   1.25 Seconds                    Modes: 20K, 10K,
Stream size:    25 Bytes                                        3.9K, 500 Ohm

Numbers in parenthesis indicate byte position in 1985 5.0 & 5.7 Litre data streams only.
Byte	Data Name	Description
1	MW2	Mode Word 2
2	PROMIDA	PROM ID (MSB)
3	PROMIDB	PROM ID (LSB)
4	ISSPMP	IAC present motor position
5	COOLDEGA	Coolant temperature, A/D counts
6	FILTMPH	Speed in Miles per hour
7	EGRDC	EGR duty cycle
8	NTRPMX	Engine speed in RPM (25 RPM per bit)
9	ADTHROT	Throttle Position, A/D counts
10	CORRCL	Base pulse (fuel) closed loop correction
11	ADO2AF	Oxygen sensor minor loop filtered value
12	MALFFLG1	Malfunction flag word 1
13	MALFFLG2	Malfunction flag word 2
14	MALFFLG3	Malfunction flag word 3
--(15)	MALFFLG4	Malfunction flag word 4
15(16)	MWFA1	Mode Word -- Fuel/Air
16(17)	MAT	Manifold air temperature
17(18)	MCUINST	MCU input status word
18(19)	LV8	Calculated load variable
19(20)	BLM	Block learn multiplier
20(21)	ALDLCNTR	Oxygen transition counter
21(--)	SAREF+1	Unlimited spark advance (Multiply by 1/2.844 for degrees)
22	DISPFLOW	Air Flow rate (Grams per sec.) MSB
23	DISPFLOW+1	Air Flow rate (Grams per sec.) LSB(1/256 grams per bit)
24	OBPINJ	Injector base pulse width MSB
25	OBPINJ+1	Injector base pulse width LSB (0.0153 Msec per bit)

Notes:

The 1985 data streams substitute ADBAT (battery voltage times ten) for LV8 as byte 18 of the data stream.

The 1986 data streams for the 5.0 Litre and the 5.7 Litre engines substitute a fourth malfunction flag (called MALFFLG4) between MALFFLG3 and MWFA1.

The 1986 data streams for the 5.0 Litre and 5.7 litre engines substitute OLDPA3 (Electronic spark cont. (knock counter input) for LV8 as byte 19 of the data stream.

The 1986 data streams for the 5.0 Litre and 5.7 litre engines do not contain the SAREF byte(s).

The 1986 data 5.0 litre and 5.7 litre engines also have an 8192 baud data stream that contains 64 bytes of data. This stream is updated once every 0.1 seconds. The definition of the flags for the 8192 baud data streams is the same as for the 160 baud data streams.

160 Baud Mode Words & Status Flag Descriptions
Byte Name	BCD Description
MALFFLG1	MALF FLAG WORD 1 Bit Code Description 0 24 Vehicle speed sensor 1 23 MAT sensor low 2 22 Throttle position sensor low 3 21 Throttle position sensor high 4 15 Coolant sensor low temperature 5 14 Coolant sensor high temperature 6 13 Oxygen sensor 7 12 No reference pulse (engine not running)
MALFFLG2	MALF FLAG WORD 2 Bit Code Description 0 42 Electronic spark timing monitor error 1 41 Cylinder select error 2 35 Not used 3 34 Mass air flow sensor low 4 33 Mass air flow sensor high 5 32 Exhaust gas recirculation diagnostic 6 31 Not used 7 25 Manifold air temperature high
MALFFLG3	MALF FLAG WORD 3 Bit Code Description 0 55 ADU error 1 54 Fuel pump voltage 2 53 Over voltage 3 52 CAL pack missing 4 51 PROM error 5 45 Oxygen sensor rich 6 44 Oxygen sensor lean 7 43 Electronic spark control failure
MW2	Mode Word 2 (160 BAUD) Bit Description 0 Road speed pulse occurred (6.25 msec check) 1 ESC failure (not used in 1986) 2 Reference pulse occurred (6.25 msec check) 3 Diagnostic switch in factory test position (3.9 K) 4 Diagnostic switch in diagnostic position (0 ohms) 5 Diagnostic switch in ALDL position (10 K ohm) 6 High battery voltage-disable MCU solenoid discretes 7 Air meter pulse occurred (6.25 msec check)
MWFA1	FUEL AIR MODE WORD 1 (160 BAUD) Bit Description 0 Fourth TPS forced O/D disable 1 Learn control enable flag (1 = enable) 2 Low battery (1 = low) 3 Prop. step taken flag (1 = rich, 0 = lean) 4 Vehicle speed sensor failure 5 EECC clow O2 rich/lean flag 6 Rich/Lean flag (1 = rich, 0 = lean) 7 Closed Loop flag (1 = Closed Loop, 0 = Open Loop)
MCUINST	MCU INPUT STATUS WORD Bit Description 0 Park/Neutral mode = 1 1 In cruise (or low A/C head pressure) = 1 2 TCC locked / or overdrive enables = 1 3 Excessive power steering pressure = 1 4 100 msec old 4th gear (set/cleared in TCC) = 1 5 Not in 3rd gear/overdrive = 1 6 4th gear switch closed = 1 (0 = in 4th gear) 7 A/C requested = 0

1986 Chevrolet 5.0 & 5.7L Port Fuel Injection (TPI) 8192 Baud ALDL data stream description
BYTE	DATA	DESCRIPTION
1	PROMIDA	First PROM ID word (MSB)
2	PROMID+1	Second PROM ID word (LSB)
3	MALFFLG1	Malfunction word 1
4	MALFFLG2	Malfunction word 2
5	MALFFLG3	Malfunction word 3
6	MALFFLG4	Malfunction word 4
7	MALLFLG5	Malfunction word 5
8	COOLDEGA	Coolant temperature (See page 3)
9	COOLTSU	Coolant temperature of start up (Same units as 8)
10	ADTHROT	Throttle position sensor (1/2.56% / bit)
11	NTRPMX	Engine speed (RPM)
12	NEWRFPER	Time between reference pulses (MSB)
13	NEWRFPER+1	Time between reference pulses (LSB)
14	FILTMPH	Vehicle speed in MPH (MSB)
15	FILTMPH+1	Vehicle speed in MPH (LSB)
16	NVATIO	RPM/MPH
17	ADO2AF	Oxygen sensor variable
18	ALDLCNTR	Oxygen sensor rich/lean transitions
19	CORRCL	Base pulse (fuel) C.L. fine correction
20	BLM	Base pulse (fuel) C.L. course correction
21	BLMCELL	Current block learn multiplier
22	INT	Closed loop integrator
23	ISSPMP	Idle speed sensor present IAC motor position
24	ISSTCD	Idle speed steps commanded direction
25	ISESDD	Desired idle speed RPM/12.5
26	FILTLVB	Filtered load variable (Air flow * RPM)
27	ADTESTCH	AD test channel (nominal: 128)(Acceptable: 118-137)
28	LVB12	Load variable 12.5 msec old
29	MAT	Manifold air temperature
30	ADMAT	Manifold air temperature
31	EGRDC	EGR duty cycle
32	PURGEDC	Charcoal cannister purge duty cycle
33	FANDC	Engine cooling fan duty cycle
34	ADBAT	Battery voltage (A/D counts: 0.1Volt/bit)
35	PPSW	fuel pump power supplied
36	DISPFLOW	Mass Air Flow variable in grams per second (MSB)
37	DISPFLOW+1	Mass Air Flow variable in grams per second (LSB)
38	AIRFLOW	Unlimited mass air flow (not defaulted)
39	SAP	Total spark advance (w.r.t. TDC) (MSB)
40	SAP + 1	Total spark advance (w.r.t. TDC) (LSB)
41	SAREF	Spark Advance w.r.t. ref. pulse (MSB)
42	SAREF+1	Spark Advance w.r.t. ref pulse (LSB)
43	OLDPA3	Electronic spark control (knock) input
44	NOCKRTD	Electronic spark control (knock) output
45	OBPINJ	Injector base pulse width (MSB)
46	OBPINJ+1	Injector base pulse width (LSB)
47	FAVAL	Total fuel/air value (MSB)
48	FAVAL +1	Total fuel/air value (LSB)
49	ACUMFUEL	Total fuel delivered (MSB)
50	ACUMFUEL+1	Total fuel delivered (LSB)
51	ACUMDIST	Total distance traveled (.0005mile/bit)
52	TIME	Engine run time (seconds) (MSB)
53	TIME+1	Engine run time (seconds) (LSB)
54	MW2	Bit status word - ALDL test condition
55	MCUINST	MCU instruction status word
56	FMDBYTE1	FMD status word
57	MW1	Mode word 1
58	NVMW	NV mode word
59	DNEEMW	Drive/neutral mode word
60	ALCLMW	ALDL mode word
61	AIRMW	AIR mode word
62	SDMW	Serial data mode word
63	MWFA1	Mode word (fuel/air)

Scaling of the Double-byte words:
WORD	DEFINITION	SCALING	COMMENTS
NEWRFPER NEWRFPER+1	Time between reference pulses	0-65535	Combine words
FILTMPH FILTMPH+1	Vehicle speed	MPH MPH/256	Whole part Fractional part
FLTLV8 FLTLV8+1	Calculated Load	LV8 LV8/256	Whole part Fractional part
DISPFLOW DISPFLOW+1	Mass Air flow value (0 if malf 33/34)	g/sec. g/sec.	Whole part Fractional part
SAP SAP+1	Unlimited spark advance w/respect to TDC	deg*2.8444	range +/- 32768
SAREF SAREF+1	Unlimited spark advance w/respect to TDC	deg*2.8444	range +/- 32768
OBPINJ OBPINJ+1	Old injector base pulse width	0.0153 msec	range 0-65536 per count
FAVAL FAVAL+1	Fuel/air ratio	6553.6/E	E = A/F ratio
ACUMFUEL ACUMFUEL+1	Accumulated fuel		running total of fuel counts
TIME TIME+1	Engine run time in seconds	secs from power up	range 0-65536

8192 Baud data stream Mode Word bit descriptions for '86 5.0 & 5.7L TPI:
Malfunction Flag BCD byte name	Definition
MALFFLG1	Bit Code Definition 0 23 MAT sensor low 1 22 Throttle sensor position low 2 21 Throttle sensor position high 3 16 Not used 4 15 Coolant sensor low temperature 5 14 Coolant temperature low sensor 6 13 Oxygen sensor 7 12 No reference pulses
MALFFLG2	Bit Code Definition 0 35 Not Used 1 34 MAF sensor low 2 33 MAF sensor high 3 32 EGR diagnostics 4 31 Not Used 5 26 Not Used 6 25 MAT sensor high 7 24 Vehicle Speed Sensor
MALFFLG3	0 51 PROM error 1 46 Not Used 2 45 Oxygen sensor rich 3 44 Oxygen sensor rich 4 43 ESC failure 5 42 EST monitor error 6 41 Cylinder select error 7 36 Burnoff diagnostics
MALFFLG4	Bit Code Definition 0 63 Not Used 1 62 Not Used 2 61 Not Used 3 55 Not Used 4 54 ADU error 5 53 Fuel pump voltage 6 52 Over voltage 7 51 CAL pack missing
MALFFLG5	Bit Code Definition 0 75 Not Used 1 74 Not Used 2 73 Not Used 3 72 Not Used 4 71 Not Used 5 66 Not Used 6 65 Not Used 7 64 Not Used

8192 Baud data stream Mode Word bit descriptions for '86 5.0 & 5.7L TPI:
Name	Description
MW2	Mode Word 2: Bit Definition 0 Overdrive (0 = off, 1 = on) 1 MALF 14 or 15 this start up 2 Reference pulse occurred (6.25 msec check) 3 In ALDL mode 8192 mode 4 (1 = in mode 4) 4 Diagnostic switch in diag. position 5 Diagnostic switch in ALDL position 6 High bttery voltage - disable MCU solenoid disabled 7 Shift light (1 = on)
MCUINST	MCU instruction word Bit Definition 0 Park/Neutral status (1 = P/N) 1 Not in 3rd gear (1 = not in 3rd) 2 Overdrive request (1 = requested) 3 Excessive power steering pressure (1 = high pressure) 4 EGR diagnostic switch closed (1 = EGR switch closed) 5 Trans. converter clutch (1 = TCC locked) 6 Air Condition high pressure (0 = high pressure) 7 Air Conditioning (0 = A/C requested)
FMDBYTE1	Bit Definition 0 Park/Neutral switch (0 = drive) 1 3rd gear 2 4th gear 3 Power steering (1 = cramp) 4 Not Used 5 EGR diagnostic 6 Air Conditioning hi-pressure 7 Air Conditioning requested (1 = A/C requested)
MW1	Mode Word 1 Bit Definition 0 Advance Flag (0 = ADV, 1 = Retard) 1 Check Engine Light delay flag 2 Interrupt service execution exc. 6.25 msec 3 Fan on disabled by PID 4 TCC road speed 1st pulse flag 5 Air cond. clutch flag (0 = A/C clutch on) 6 Bypass check enable 7 Engine running flag ( 1 = running)
NVMW	Bit Definition 0 O2 sensor ready (1 = ready) 1 Closed loop timer timed out (1 = timed out) 2 Not used 3 Improper shutdown (1 = yes) 4 CCP startup timer expired (1 = expired) 5 IAC kickdown enabled ( 1 = enabled) 6 KWARM kickdown enabled (1 = enabled) 7 MALF 42 failed (EST monitor) (1 = failed)
DNEEMW	Bit Definition 0 Overdrive on (1 = on) 1 1st gear direct (1 =on) 2 1st upshift OK (look-ahead) ( 1 = ok) 3 4th gear (1 = 4th gear) 4 1st gear overdrive (1 = overdrive) 5 Downshift/off request (1 = request) 6 Upshift/on request (1=request) 7 Overdrive active (1 =request)
ALDLMW	ALDL Mode Word Bit Definition 0 ALDL reset 1 Not Used 2 Field Service mode 3 First C/L pass-thru field service mode (1 = done) 4 Field service O2 transition 5 One second flag 6 200 MSEC toggle bit for 2.5 HZ flash rate 7 Pullup resistor for coolant (1 = 4K)
AIRMW	Air mode word Bit Definition 0 100 MS old CCP purge on flag (1 = on) 1 Air management (0 = air diverted) 2 Air switched port (1 = switched) 3 Not Used 4 Skip burnoff due to >17 Volts (1 = skip) 5 D.E. QSEQ (1 = on) 6 Burn off air meter (1 = burn off) 7 Decel enleanment (1 = enleanment)
SDMW	Serial data mode word Bit Definition 0 Expecting first 160 BAUD interrupt (1 = yes) 1 Expecting second 160 BAUD interrupt (1 = yes) 2 In 8192 Mode (1 = yes) 3 Locked in 8192 mode (1 = yes) 4 Not used 5 Not used 6 Not used 7 Not used
MWFA1	Mode Word Fuel/Air Bit Definition 0 Nor used 1 Learn control enable flag (1 = enable store) 2 Not used 3 Not used 4 Vehicle speed sensor failure 5 EECC clos O2 Rich/Lean flag 6 Rich-lean flag (1 = rich) 7 Closed loop flag (1 = closed loop)