Onboard Diagnostics - Differences by year

[RobertISaar]

i can only speak with 100% accuracy for OBD1/1.5 60V6 motors and their electronics, but i will try and get the basics for the 3800 and 4 cylinder cars as well.

code masks:

2.8 LB6
1988-1989 $6D

there was a bulletin posted ~June-September of 1989 for 1988 cars that disabled the MAF and essentially turned it into an IAT sensor. the BCC's of the revised PROMs are ASWH, ATRA, ASWJ, ASWL, ASWK.

3.1 LH0
1989 $6D
1990 $88
1991-1992 $A1
1993-1994 $DF

3.1 Turbo LG5
1989-1990 $8F

3100 L82
1993 unknown
1994-1995 unknown

3.4 LQ1
1991-1993 $DF
1994-1995 $2E

Quad4 LD2
1990 $8B
1991 should be $A8

2.2MPFI LN2
1993 unknown.

2.5TBI LR8
1990 $89
1991-1992 probably $89

3800 S1 L27
1991-1992 $5B5
1993 $F5
1994-1995 $5B7

ECM/PCM Part Numbers

LB6, LH0 (89-92), LG5, LR8 - 1227727
LQ1, LH0 (93-94) - 16149396
L82 (93) - 16184164
L82 (94-95) - 16196397
L27 (91-92) - 16132792 or 16141470
L27 (93) - 16177107 or 16141470
L27 (94-95) - 16183247
LD2 - 1228707 or 1228708
LN2 - unknown

[RobertISaar]

this may be useful for anyone that has to replace their ECM/MEMCAL...

arrows indicate that an updated tune was released from the factory. it would be best to match them exactly, but as long as it fits the situation, it will probably work well enough to run/drive but you may lose other functions...

no notes means it's your average LQ1 + 4T60-E with federal emissions...

EDIT: here's all of the ones i could think of that apply to OBD1 W's...

LB6: unless otherwise marked, assume 4T60, federal emissions
3800: unless otherwise marked, assume 4T60, federal emissions
LH0: unless otherwise marked, assume 4T60, federal emissions
2E: unless otherwise marked, assume federal emissions
Quad4: unless otherwise marked, assume TH125C, federal emissions...

EDIT2:

forogt about LG5/LR8/LN2...

all LG5 are 4T60
all LR8 are TH125C
all LN2 are TH125C

emissions are federal unless noted otherwise.