1991 Corvette CCM to ECM Communication Questions

[vettxtc]

I have a 1991 Corvette. I was wondering if anyone knew what type of information the CCM is expecting from the ECM in order to talk to it.

Reason I ask is I would like to install a 1992 CCM in my vette to be able to use the different style LCD for the speedo and fuel. If I just install the CCM and LCD it will work, but I keep getting a code stating it cannot find the ECM. If I could either modify the code of the CCM or ECM I think I it would work.

Also does anyone know if the data stream for both an L98 (727 ECM) and the 1992 LT1 is similar? meaning the Coolant temp and oil temp are at the same addressses for both?

Thanks

[Casey]

You will have to make your 91 PCM look like a 92.

Here is the datastream for the 92/93 CCM.


[tt]
DATA STREAM A173 SPECIFICATION

SPECIFICATIONS FOR DATA STREAM INFORMATION
-------------------------------------------

CCM USAGE:
1992 "Y" CAR WITH 5.7L (LT1) (VIN=P) AND 5.7L (LT5) (VIN=J)
1993 "Y" CAR WITH 5.7L (LT1) (VIN=P) AND 5.7L (LT5) (VIN=J)

DATA PIN : READ DATA ON PIN "M" OF ALDL CONNECTOR

BAUD RATE : 8192 BAUD - BI-DIRECTIONAL

MODE 0 (RETURN TO NORMAL MODE)
ALDL REQUEST:
- MESSAGE ID = $F1
- MESSAGE LENGTH = $56
- MODE = $00
- CHECKSUM


F0 POLL (CCM ALDL DEVICE PRESENCE CHECK)
- MESSAGE ID = $F0
- MESSAGE LENGTH = $56
- CCM ID = $F1
- CHECKSUM



MODE 1 (TRANSMIT MESSAGE 0)
ALDL REQUEST:
- MESSAGE ID = $F1
- MESSAGE LENGTH = $57
- MODE = $01
- MESSAGE NUMBER = $00
- CHECKSUM

THE CCM RESPONDS WITH THE FOLLOWING MESSAGE:
- MESSAGE ID = $F1
- MESSAGE LENGTH = $7A
- MODE = $01
- DATA BYTE 1
.
.
- DATA BYTE 36
- CHECKSUM

MODE 1 (TRANSMIT MESSAGE 1)
ALDL REQUEST:
- MESSAGE ID = $F1
- MESSAGE LENGTH = $57
- MODE = $01
- MESSAGE NUMBER = $01
- CHECKSUM

THE CCM RESPONDS WITH THE FOLLOWING MESSAGE:
- MESSAGE ID = $F1
- MESSAGE LENGTH = $6D
- MODE = $01
- DATA BYTE 1
.
.
- DATA BYTE 23
- CHECKSUM

MODE 7 (COMMAND MESSAGE)
ALDL REQUEST:
- MESSAGE ID = $F1
- MESSAGE LENGTH = $57
- MODE = $07
- MESSAGE CODE = $10
- CHECKSUM

THE CCM RESPONDS BY TRANSMITTING THE NORMAL MODE MESSAGE



MODE 8 (DISABLE COMMUNICATIONS)
ALDL REQUEST:
- MESSAGE ID = $F1
- MESSAGE LENGTH = $56
- MODE = $08
- CHECKSUM



MODE 9 (ENABLE COMMUNICATIONS)
ALDL REQUEST:
- MESSAGE ID = $F1
- MESSAGE LENGTH = $56
- MODE = $09
- CHECKSUM


MODE 10 (CLEAR MALFUNCTION CODES)
ALDL REQUEST:
- MESSAGE ID = $F1
- MESSAGE LENGTH = $56
- MODE = $0A
- CHECKSUM



CCM ALDL DATA LIST 
NUMBER OF DATA WORDS - 36
CCM ALDL MODE 1 DATA LIST (MESSAGE 0)
BYTE BIT DESCRIPTION
---- --- -------------
1 0-2 UNIVERSAL THEFT DETERRENT STATE
0 = PASSIVE
1 = ACTIVE
2 = DOORS ARMED
3 = DOORS AND HATCH ARMED
4 = ALARM
5 = ALARM TIMED OUT
3 FEDS FUEL ENABLE 0 = DISABLE 1 = ENABLE
4 ENGLISH/METRIC STATUS 0 = ENGLISH 1 = METRIC
5 CURRENT FAULT 0 = NO 1 = YES
6 LCD UPDATE RATE 0 = SLOW 1 = FAST
7 SPARE

2 0 DOOR KEY SWITCH 0 = NORMAL 1 = UNLOCK
1 RIGHT DOOR AJAR 0 = CLOSED 1 = OPEN
2 LEFT DOOR AJAR 0 = CLOSED 1 = OPEN
3 KEY IN IGNITION 0 = NO 1 = YES
4 HATCH AJAR 0 = CLOSED 1 = OPEN
5 POWER DOOR UNLOCK 0 = NO 1 = YES
6 POWER DOOR LOCK 0 = NO 1 = YES
7 SPARE

3 0 PARKING LIGHTS 0 = OFF 1 = ON
1 REAR DEFOG 0 = OFF 1 = ON
2 SEAT BELT SWITCH 0 = OFF 1 = ON
3 HIGH BEAM 0 = OFF 1 = ON
4 NOT USED
5 OIL LEVEL SWITCH 0 = LOW 1 = NORMAL
6-7 SPARE

4 0 IGNITION 3 PRESENT 0 = NO 1 = YES
1 IGNITION 1 PRESENT 0 = NO 1 = YES
2 DIAGNOSTIC ENABLE 0 = DISABLE 1 = ENABLE
3 SPARE
4 FASTEN SEAT BELTS INPUT 0 = INACTIVE 1 = ACTIVE
5-7 SPARE

5 0 CHANGE OIL TELLTALE 0 = OFF 1 = ON
1 CHECK GAGES TELLTALE 0 = OFF 1 = ON
2 FASTEN SEAT BELT TELLTALE 0 = OFF 1 = ON
3 SECURITY LAMP TELLTALE 0 = OFF 1 = ON
4 SPARE
5 HIGH BEAM INDICATOR DIM 0 = 60% 1 = 100%
6 OIL LEVEL TELLTALE 0 = OFF 1 = ON
7 SPARE
6 0 LCD BLANKING CONTROL 0 = OFF 1 = ON
1 HORN RELAY 0 = OFF 1 = ON
2 REAR DEFOG RELAY 0 = OFF 1 = ON
3 COURTESY LAMP RELAY 0 = OFF 1 = ON
4 CRANK RELAY 0 = OFF 1 = ON
5 CHIME 0 0 = OFF 1 = ON
6 CHIME 1 0 = OFF 1 = ON
7 SPARE
7 0 LCD BLANKING CONTROL-FDBK 0 = OFF 1 = ON
1 HORN RELAY-FDBK 0 = OFF 1 = ON
2 REAR DEFOG RELAY-FDBK 0 = OFF 1 = ON
3 COURTESY LAMP RELAY-FDBK 0 = OFF 1 = ON
4 CRANK RELAY-FDBK 0 = OFF 1 = ON
5-7 SPARE

8 DIC SWITCH A/D COUNTS N = COUNTS (SEE TABLE 1)
9 UNFILTERED FUEL LEVEL GAL = N*.1
10 FILTERED DIMMING POTENTIOMETER N = COUNTS
11 VATS KEY A/D COUNTS N = COUNTS (SEE TABLE 2)
12 AMBIENT LIGHT SENSOR A/D COUNTS N = COUNTS
13 VEHICLE SPEED MPH = N IF BYTE1 BIT4 CLEAR
KPH = N*1.609 IF BYTE1 BIT4 SET
14 IGNITION STATUS VOLTS = N*.1
15 SWITCHED BATTERY VOLTAGE VOLTS = N*.1
16 CLUSTER GAGE BACKLIGHT DIMMING PWM %DUTY CYCLE = N
17 CLUSTER LCD BACKLIGHT DIMMING PWM %DUTY CYCLE = N
18 HVAC AND RADIO LCD BACKLIGHT DIMMING %DUTY CYCLE = N
19 LED INDICATOR DIMMING PWM %DUTY CYCLE = N
20 SEASON ODOMETER MSB
21 SEASON ODOMETER LSB MILES = ([N20]*250+[N21])*16
22 OIL MONITOR EFFECTIVE REVOLUTION TO SERVICE COUNTER
REVOLUTIONS = N*100,000
23 REAR DEFOG TIMER SECONDS = N*5
24 COURTESY LAMP TIMER SECONDS = N

25 CURRENT MALFUNCTION WORD 1
0 MALF CODE 22 1 = DEFOG RELAY COIL SHORT-BAT/OPEN CCM
1 MALF CODE 21 1 = HORN RELAY COIL SHORT-BAT/OPEN CCM
2 NOT USED
3 MALF CODE 16 1 = IGNITION 3 FUSE BLOWN OR MISSING
4 MALF CODE 15 1 = FUEL LEVEL SENSOR OPEN/SHORT TO BAT
5 MALF CODE 14 1 = DIC SWITCH SHORTED TO GROUND
6 MALF CODE 13 1 = DIC SWITCH OPEN/SHORT TO BAT
7 MALF CODE 12 1 = NO MALFUNCTION CODE STORED

26 CURRENT MALFUNCTION WORD 2
0 MALF CODE 31 1 = LCD DATA SHORT TO BAT/OPEN CCM
1 NOT USED
2 NOT USED
3 MALF CODE 27 1 = LCD BLANKING CTL SHORT TO GND/OPEN
4 MALF CODE 26 1 = LCD BLANKING CTL SHORT-BAT/OPEN CCM
5 MALF CODE 25 1 = CTSY RELAY COIL SHORT TO GND/OPEN
6 MALF CODE 24 1 = CTSY RELAY COIL SHORT-BAT/OPEN CCM
7 MALF CODE 23 1 = DEFOG RELAY COIL SHORT IT GND/OPEN
27 CURRENT MALFUNCTION WORD 3
0 MOT USED
1 MALF CODE 38 1 = M CLOCK SHORT TO GND/OPEN
2 MALF CODE 37 1 = M CLOCK SHORT-BAT/OPEN CCM
3 MALF CODE 36 1 = DATA STROBE SHORT TO GND/OPEN
4 MALF CODE 35 1 = DATA STROBE SHORT-BAT/OPEN CCM
5 MALF CODE 34 1 = DATA CLOCK SHORT TO GND/OPEN
6 MALF CODE 33 1 = DATA CLOCK SHORT-BAT/OPEN CCM
7 MALF CODE 32 1 = LCD DATA SHORT TO GND/OPEN
28 CURRENT MALFUNCTION WORD 4
0 MALF CODE 54 1 = VATS FUEL ENABLE FAILURE
1 MALF CODE 53 1 = VATS OPEN KEY CIRCUIT DETECTION
2 MALF CODE 52 1 = VATS SHORTED KEY CIRCUIT DETECTION
3 MALF CODE 51 1 = VATS INVALID KEY DETECTION
4 NOT USED
5 NOT USED
6 NOT USED
7 MALF CODE 41 1 = LOSS OF ECM SERIAL DATA

29 CURRENT MALFUNCTION WORD 5
0 NOT USED
1 NOT USED
2 NOT USED
3 MALF CODE 63 1 = VATS KEY #2 RESISTANCE TOO LOW
4 MALF CODE 62 1 = VATS KEY #2 RESISTANCE TOO HIGH
5 MALF CODE 61 1 = VATS KEY #1 RESISTANCE OUT OF RANGE
6 NOT USED
7 NOT USED

30 CURRENT MALFUNCTION WORD 6
0 NOT USED
1 NOT USED
2 NOT USED
3 MALF CODE 74 1 = LED DIM PWM OUTPUT SHORT TO GND/OPEN
4 MALF CODE 73 1 = LED DIM PWM OUTPUT SHORT-BAT/OPEN CCM
5 MALF CODE 72 1 = VF DIM PWM OUTPUT SHORT TO GND/OPEN
6 MALF CODE 71 1 = VF DIM PWM OUTPUT SHORT-BAT/OPEN CCM
7 NOT USED

31 HISTORY MALFUNCTION WORD 1
0 HIST MALF CODE 22 1 = DEFOG RELAY COIL SHORT-BAT/OPEN CCM
1 HIST MALF CODE 21 1 = HORN RELAY COIL SHORT-BAT/OPEN CCM
2 NOT USED
3 MALF CODE 16 1 = IGNITION 3 FUSE BLOWN OR MISSING
4 HIST MALF CODE 15 1 = FUEL LEVEL SENSOR OPEN/SHORT TO BAT
5 HIST MALF CODE 14 1 = DIC SWITCH SHORTED TO GROUND
6 HIST MALF CODE 13 1 = DIC SWITCH OPEN/SHORT TO BAT
7 HIST MALF CODE 12 1 = NO MALFUNCTION CODE STORED

32 HISTORY MALFUNCTION WORD 2
0 HIST MALF CODE 31 1 = LCD DATA SHORT TO BAT/OPEN CCM
1 NOT USED
2 NOT USED
3 HIST MALF CODE 27 1 = LCD BLANKING CTL SHORT TO GND/OPEN
4 HIST MALF CODE 26 1 = LCD BLANKING CTL SHORT-BAT/OPEN CCM
5 HIST MALF CODE 25 1 = CTSY RELAY COIL SHORT TO GND/OPEN
6 HIST MALF CODE 24 1 = CTSY RELAY COIL SHORT-BAT/OPEN CCM
7 HIST MALF CODE 23 1 = DEFOG RELAY COIL SHORT IT GND/OPEN
..page
33 HISTORY MALFUNCTION WORD 3
0 NOT USED
1 HIST MALF CODE 38 1 = M CLOCK SHORT TO GND/OPEN
2 HIST MALF CODE 37 1 = M CLOCK SHORT-BAT/OPEN CCM
3 HIST MALF CODE 36 1 = DATA STROBE SHORT TO GND/OPEN
4 HIST MALF CODE 35 1 = DATA STROBE SHORT-BAT/OPEN CCM
5 HIST MALF CODE 34 1 = DATA CLOCK SHORT TO GND/OPEN
6 HIST MALF CODE 33 1 = DATA CLOCK SHORT-BAT/OPEN CCM
7 HIST MALF CODE 32 1 = LCD DATA SHORT TO GND/OPEN

34 HISTORY MALFUNCTION WORD 4
0 HIST MALF CODE 54 1 = VATS FUEL ENABLE FAILURE
1 HIST MALF CODE 53 1 = VATS OPEN KEY CIRCUIT DETECTION
2 HIST MALF CODE 52 1 = VATS SHORTED KEY CIRCUIT DETECTION
3 HIST MALF CODE 51 1 = VATS INVALID KEY DETECTION
4 NOT USED
5 NOT USED
6 NOT USED
7 HIST MALF CODE 41 1 = LOSS OF ECM SERIAL DATA

35 HISTORY MALFUNCTION WORD 5
0 NOT USED
1 NOT USED
2 NOT USED
3 HIST MALF CODE 63 1 = VATS KEY #2 RESISTANCE TOO LOW
4 HIST MALF CODE 62 1 = VATS KEY #2 RESISTANCE TOO HIGH
5 HIST MALF CODE 61 1 = VATS KIY #1 RESISTANCE OUT OF RANGE
6 NOT USED
7 NOT USED

36 HISTORY MALFUNCTION WORD 6
0 NOT USED
1 NOT USED
2 NOT USED
3 NOT USED
4 NOT USED
5 HIST MALF CODE 72 1 = VF DIM PWM OUTPUT SHORT TO GND/OPEN
6 HIST MALF CODE 71 1 = VF DIM PWM OUTPUT SHORT-BAT/OPEN CCM[/tt]


[tt]
DATA STREAM A111 SPECIFICATION

SPECIFICATIONS FOR DATA STREAM INFORMATION
-------------------------------------------

CCM USAGE:
1990 "Y" CAR WITH 5.7L (L98) (VIN=8) AND 5.7L (LT5) (VIN=J)
1991 "Y" CAR WITH 5.7L (L98) (VIN=8) AND 5.7L (LT5) (VIN=J)


DATA PIN : READ DATA ON PIN "M" OF ALDL CONNECTOR

BAUD RATE : 8192 BAUD - BI-DIRECTIONAL

..PAGE
MODE 0 (RETURN TO NORMAL MODE)
ALDL REQUEST:
- MESSAGE ID = $F1
- MESSAGE LENGTH = $56
- MODE = $00
- CHECKSUM

CCM RESPONSE:
CCM BROADCAST MESSAGE
- MESSAGE ID = $10
- MESSAGE LENGTH = $59
- STATUS WORD
BIT DESCRIPTION
0 ENGLISH/METRIC STATUS 0 = ENGLISH 1 = METRIC
1 ENGINE 0 = L98 1 = LT5
2 A/C CLUTCH STATUS 0 = OFF 1 = ON
3 SPARE
4 SPARE
5 SPARE
6 SPARE
7 SPARE

- COOLANT TEMPERATURE
DEG C = N*.75 - 40
- ENGINE RPM
RPM = N*25
- VEHICLE SPEED
MPH = N
- CHECKSUM


NOTE: THE BROADCAST MESSAGE IS USED TO SUPPLY INFORMATION TO
RECEIVE ONLY REMOTE SYSTEMS.



CCM ALDL DEVICE PRESENCE CHECK
- MESSAGE ID = $F0
- MESSAGE LENGTH = $56
- CCM ID = $F1
- CHECKSUM



..PAGE
MODE 1 (TRANSMIT MESSAGE 0)
ALDL REQUEST:
- MESSAGE ID = $F1
- MESSAGE LENGTH = $57
- MODE = $01
- MESSAGE NUMBER = $00
- CHECKSUM

THE CCM RESPONDS WITH THE FOLLOWING MESSAGE:
- MESSAGE ID = $F1
- MESSAGE LENGTH = $7A
- MODE = $01
- DATA BYTE 1
.
.
- DATA BYTE 36
- CHECKSUM

MODE 1 (TRANSMIT MESSAGE 1)
ALDL REQUEST:
- MESSAGE ID = $F1
- MESSAGE LENGTH = $57
- MODE = $01
- MESSAGE NUMBER = $01
- CHECKSUM

THE CCM RESPONDS WITH THE FOLLOWING MESSAGE:
- MESSAGE ID = $F1
- MESSAGE LENGTH = $6D
- MODE = $01
- DATA BYTE 1
.
.
- DATA BYTE 23
- CHECKSUM

..PAGE
MODE 7 (COMMAND MESSAGE)
ALDL REQUEST:
- MESSAGE ID = $F1
- MESSAGE LENGTH = $57
- MODE = $07
- MESSAGE CODE = $10
- CHECKSUM

THE CCM RESPONDS BY TRANSMITTING THE NORMAL MODE MESSAGE



MODE 8 (DISABLE COMMUNICATIONS)
ALDL REQUEST:
- MESSAGE ID = $F1
- MESSAGE LENGTH = $56
- MODE = $08
- CHECKSUM



MODE 9 (ENABLE COMMUNICATIONS)
ALDL REQUEST:
- MESSAGE ID = $F1
- MESSAGE LENGTH = $56
- MODE = $09
- CHECKSUM


MODE 10 (CLEAR MALFUNCTION CODES)
ALDL REQUEST:
- MESSAGE ID = $F1
- MESSAGE LENGTH = $56
- MODE = $0A
- CHECKSUM



..HEAD02L CCM ALDL DATA LIST
..HEAD03L NUMBER OF DATA WORDS - 36
..HEAD04L CCM ALDL MODE 1 DATA LIST (MESSAGE 0)
BYTE BIT DESCRIPTION
---- --- -------------
1 0-2 UNIVERSAL THEFT DETERRENT STATE
0 = PASSIVE
1 = ACTIVE
2 = DOORS ARMED
3 = DOORS AND HATCH ARMED
4 = ALARM
5 = ALARM TIMED OUT
3 VATS FUEL ENABLE 0 = DISABLE 1 = ENABLE
4 ENGLISH/METRIC STATUS 0 = ENGLISH 1 = METRIC
5 CURRENT FAULT 0 = NO 1 = YES
6 LCD UPDATE RATE 0 = SLOW 1 = FAST
7 SPARE

2 0 DOOR KEY SWITCH 0 = NORMAL 1 = UNLOCK
1 RIGHT DOOR AJAR 0 = CLOSED 1 = OPEN
2 LEFT DOOR AJAR 0 = CLOSED 1 = OPEN
3 KEY IN IGNITION 0 = NO 1 = YES
4 HATCH AJAR 0 = CLOSED 1 = OPEN
5 POWER DOOR UNLOCK 0 = NO 1 = YES
6 POWER DOOR LOCK 0 = NO 1 = YES
7 SPARE

3 0 PARKING LIGHTS 0 = OFF 1 = ON
1 REAR DEFOG 0 = OFF 1 = ON
2 SEAT BELT SWITCH 0 = OFF 1 = ON
3 HIGH BEAM 0 = OFF 1 = ON
4 AMBIENT TEMPERATURE SWITCH 0 = COLD 1 = WARM
5 OIL LEVEL SWITCH 0 = LOW 1 = NORMAL
6-7 SPARE

4 0 IGNITION 3 PRESENT 0 = NO 1 = YES
1 IGNITION 1 PRESENT 0 = NO 1 = YES
2 DIAGNOSTIC ENABLE 0 = DISABLE 1 = ENABLE
3 SPARE
4 FASTEN SEAT BELTS INPUT 0 = INACTIVE 1 = ACTIVE
5-7 SPARE
..PAGE
5 0 CHANGE OIL TELLTALE 0 = OFF 1 = ON
1 CHECK GAGES TELLTALE 0 = OFF 1 = ON
2 FASTEN SEAT BELT TELLTALE 0 = OFF 1 = ON
3 SECURITY LAMP TELLTALE 0 = OFF 1 = ON
* 4 DELAYED ACCESSORY BUS 0 = OFF 1 = ON
5 HIGH BEAM INDICATOR DIM 0 = 60% 1 = 100%
6 OIL LEVEL TELLTALE 0 = OFF 1 = ON
7 SPARE
NOTE: The * denotes that the variable is available on 91 CCM only.

6 0 LCD BLANKING CONTROL 0 = OFF 1 = ON
1 HORN RELAY 0 = OFF 1 = ON
2 REAR DEFOG RELAY 0 = OFF 1 = ON
3 COURTESY LAMP RELAY 0 = OFF 1 = ON
4 CRANK RELAY 0 = OFF 1 = ON
5 CHIME 0 0 = OFF 1 = ON
6 CHIME 1 0 = OFF 1 = ON
7 SPARE

7 0 LCD BLANKING CONTROL-FDBK 0 = OFF 1 = ON
1 HORN RELAY-FDBK 0 = OFF 1 = ON
2 REAR DEFOG RELAY-FDBK 0 = OFF 1 = ON
3 COURTESY LAMP RELAY-FDBK 0 = OFF 1 = ON
4 CRANK RELAY-FDBK 0 = OFF 1 = ON
5-7 SPARE

8 DIC SWITCH A/D COUNTS N = COUNTS (SEE TABLE 1)
9 UNFILTERED FUEL LEVEL GAL = N*.1
10 FILTERED DIMMING POTENTIOMETER N = COUNTS
11 VATS KEY A/D COUNTS N = COUNTS (SEE TABLE 2)
12 AMBIENT LIGHT SENSOR A/D COUNTS N = COUNTS
13 VEHICLE SPEED MPH = N IF BYTE1 BIT4 CLEAR
KPH = N*1.609 IF BYTE1 BIT4 SET
14 IGNITION STATUS VOLTS = N*.1
15 SWITCHED BATTERY VOLTAGE VOLTS = N*.1
16 CLUSTER GAGE BACKLIGHT DIMMING PWM %DUTY CYCLE = N
17 CLUSTER LCD BACKLIGHT DIMMING PWM %DUTY CYCLE = N
18 HVAC AND RADIO LCD BACKLIGHT DIMMING %DUTY CYCLE = N
19 LED INDICATOR DIMMING PWM %DUTY CYCLE = N
20 SEASON ODOMETER MSB
21 SEASON ODOMETER LSB MILES = ([N20]*250+[N21])*16
..PAGE
22 OIL MONITOR EFFECTIVE REVOLUTION TO SERVICE COUNTER
REVOLUTIONS = N*100,000
23 REAR DEFOG TIMER SECONDS = N*5
24 COURTESY LAMP TIMER SECONDS = N

25 0 MALF CODE 22 1 = DEFOG RELAY COIL SHORT-BAT/OPEN CCM
1 MALF CODE 21 1 = HORN RELAY COIL SHORT-BAT/OPEN CCM
2 NOT USED
3 NOT USED
****** 4 MALF CODE 15 1 = FUEL LEVEL SENSOR OPEN/SHORT TO BAT MASKED OUT
5 MALF CODE 14 1 = DIC SWITCH SHORTED TO GROUND
6 MALF CODE 13 1 = DIC SWITCH OPEN/SHORT TO BAT
7 MALF CODE 12 1 = NO MALFUNCTION CODE STORED
26 0 MALF CODE 31 1 = LCD DATA SHORT TO BAT/OPEN CCM
1 NOT USED
2 NOT USED
3 MALF CODE 27 1 = LCD BLANKING CTL SHORT TO GND/OPEN
4 MALF CODE 26 1 = LCD BLANKING CTL SHORT-BAT/OPEN CCM
5 MALF CODE 25 1 = CTSY RELAY COIL SHORT TO GND/OPEN
6 MALF CODE 24 1 = CTSY RELAY COIL SHORT-BAT/OPEN CCM
****** 7 MALF CODE 23 1 = DEFOG RELAY COIL SHORT IT GND/OPEN MASKED OUT

27 0 MOT USED
1 MALF CODE 38 1 = M CLOCK SHORT TO GND/OPEN
2 MALF CODE 37 1 = M CLOCK SHORT-BAT/OPEN CCM
3 MALF CODE 36 1 = DATA STROBE SHORT TO GND/OPEN
4 MALF CODE 35 1 = DATA STROBE SHORT-BAT/OPEN CCM
5 MALF CODE 34 1 = DATA CLOCK SHORT TO GND/OPEN
6 MALF CODE 33 1 = DATA CLOCK SHORT-BAT/OPEN CCM
7 MALF CODE 32 1 = LCD DATA SHORT TO GND/OPEN

28 0 MALF CODE 54 1 = VATS FUEL ENABLE FAILURE
1 MALF CODE 53 1 = VATS OPEN KEY CIRCUIT DETECTION
2 MALF CODE 52 1 = VATS SHORTED KEY CIRCUIT DETECTION
3 MALF CODE 51 1 = VATS INVALID KEY DETECTION
4 NOT USED
5 NOT USED
6 NOT USED
7 MALF CODE 41 1 = LOSS OF ECM SERIAL DATA

29 0 NOT USED
1 MALF CODE 65 1 = VATS KEY #3 RESISTANCE TOO LOW
2 MALF CODE 64 1 = VATS KEY #3 RESISTANCE TOO HIGH
3 MALF CODE 63 1 = VATS KEY #2 RESISTANCE TOO LOW
4 MALF CODE 62 1 = VATS KEY #2 RESISTANCE TOO HIGH
5 MALF CODE 61 1 = VATS KEY #1 RESISTANCE OUT OF RANGE
6 NOT USED
7 NOT USED
..PAGE
30 0 NOT USED
1 NOT USED
2 NOT USED
3 MALF CODE 74 1 = LED DIM PWM OUTPUT SHORT TO GND/OPEN
4 MALF CODE 73 1 = LED DIM PWM OUTPUT SHORT-BAT/OPEN CCM
5 MALF CODE 72 1 = VF DIM PWM OUTPUT SHORT TO GND/OPEN
6 MALF CODE 71 1 = VF DIM PWM OUTPUT SHORT-BAT/OPEN CCM
7 NOT USED

31 0 HIST MALF CODE 22 1 = DEFOG RELAY COIL SHORT-BAT/OPEN CCM
1 HIST MALF CODE 21 1 = HORN RELAY COIL SHORT-BAT/OPEN CCM
2 NOT USED
3 NOT USED
4 HIST MALF CODE 15 1 = FUEL LEVEL SENSOR OPEN/SHORT TO BAT
5 HIST MALF CODE 14 1 = DIC SWITCH SHORTED TO GROUND
6 HIST MALF CODE 13 1 = DIC SWITCH OPEN/SHORT TO BAT
7 HIST MALF CODE 12 1 = NO MALFUNCTION CODE STORED

32 0 HIST MALF CODE 31 1 = LCD DATA SHORT TO BAT/OPEN CCM
1 NOT USED
2 NOT USED
3 HIST MALF CODE 27 1 = LCD BLANKING CTL SHORT TO GND/OPEN
4 HIST MALF CODE 26 1 = LCD BLANKING CTL SHORT-BAT/OPEN CCM
5 HIST MALF CODE 25 1 = CTSY RELAY COIL SHORT TO GND/OPEN
6 HIST MALF CODE 24 1 = CTSY RELAY COIL SHORT-BAT/OPEN CCM
7 HIST MALF CODE 23 1 = DEFOG RELAY COIL SHORT IT GND/OPEN

33 0 NOT USED
1 HIST MALF CODE 38 1 = M CLOCK SHORT TO GND/OPEN
2 HIST MALF CODE 37 1 = M CLOCK SHORT-BAT/OPEN CCM
3 HIST MALF CODE 36 1 = DATA STROBE SHORT TO GND/OPEN
4 HIST MALF CODE 35 1 = DATA STROBE SHORT-BAT/OPEN CCM
5 HIST MALF CODE 34 1 = DATA CLOCK SHORT TO GND/OPEN
6 HIST MALF CODE 33 1 = DATA CLOCK SHORT-BAT/OPEN CCM
7 HIST MALF CODE 32 1 = LCD DATA SHORT TO GND/OPEN

34 0 HIST MALF CODE 54 1 = VATS FUEL ENABLE FAILURE
1 HIST MALF CODE 53 1 = VATS OPEN KEY CIRCUIT DETECTION
2 HIST MALF CODE 52 1 = VATS SHORTED KEY CIRCUIT DETECTION
3 HIST MALF CODE 51 1 = VATS INVALID KEY DETECTION
4 NOT USED
5 NOT USED
6 NOT USED
7 HIST MALF CODE 41 1 = LOSS OF ECM SERIAL DATA

35 0 NOT USED
1 HIST MALF CODE 65 1 = VATS KEY #3 RESISTANCE TOO LOW
2 HIST MALF CODE 64 1 = VATS KEY #3 RESISTANCE TOO HIGH
3 HIST MALF CODE 63 1 = VATS KEY #2 RESISTANCE TOO LOW
4 HIST MALF CODE 62 1 = VATS KEY #2 RESISTANCE TOO HIGH
5 HIST MALF CODE 61 1 = VATS KEY #1 RESISTANCE OUT OF RANGE
6 NOT USED
7 NOT USED
..PAGE
36 0 NOT USED
1 NOT USED
2 NOT USED
3 NOT USED
4 NOT USED
5 HIST MALF CODE 72 1 = VF DIM PWM OUTPUT SHORT TO GND/OPEN
6 HIST MALF CODE 71 1 = VF DIM PWM OUTPUT SHORT-BAT/OPEN CCM
7 NOT USED[/tt]
Ken

[vettxtc]

Thanks for the Info Ken,

next question, how do I capture the data stream for the 1991 CCM?

Then how can I find the right spot to change on the 91 PCM to work with the CCM. I am still learning the hwo to read the coding like what you posted so any help would be great!!.

Thanks
Jeff

[Casey]

Well in order to get this to work correctly you will need to know what the device ID is of each CCM and ECM.

They will respond to different $ID message requests.

You will then have to make sure the datastream request returns the correct number of bytes (returned message length) as well. Otherwise the checksum byte will be in the wrong location and the message will be ignored.

This is not an easy job for a beginner, but can be done. It's more time consuming than anything else. I have not compared the 91 to 92 datastreams, and I doubt this will be a single byte change (fix) to get them to talk.


I don't think anybody makes OBDI raw datastream display software.

If you don't mind waiting, we may be able to whip something up.


Ken

[vettxtc]

Well in order to get this to work correctly you will need to know what the device ID is of each CCM and ECM.

They will respond to different $ID message requests.

You will then have to make sure the datastream request returns the correct number of bytes (returned message length) as well. Otherwise the checksum byte will be in the wrong location and the message will be ignored.

This is not an easy job for a beginner, but can be done. It's more time consuming than anything else. I have not compared the 91 to 92 datastreams, and I doubt this will be a single byte change (fix) to get them to talk.


I don't think anybody makes OBDI raw datastream display software.

If you don't mind waiting, we may be able to whip something up.


Ken

Ken, I don't mind waiting at all. I am starting to understand some of the terms too. It just takes time to learn it all

Now, how would I be able to find out the $ID for the ECMs? I know the CCM is master and the ECM, ABS ECM and A/C all connect on the serial line as well. Would the GM Service manual have any of this info? i have the 1991 and 1992 Service manuals, I have a 1992 speedo LCD and CCM as well as my 1991 stuff in the car.

Let me know what you come up with.. If I need to make any hardware pieces (like a cable) let me know, I can do that stuff..