| Re: 86-89 Digital Instrument Cluster "OD" light |
Subject: Re: 86-89 Digital Instrument Cluster "OD" light by tequilaboy on 2012/12/12 20:51:16 I suspect that the OD indicator in the 87-88 specific cluster is controlled via serial data rather than a hardwired pin. Edit: Got abit ahead of myself. Same idea, different bit. Must be in the 160 baud data stream. TCC bit 5 seems to fit the bill. $32B data: LC7CD FDB $0037 ; 55 MCU INPUT STATUS WORD ; ; Bit 0 = PARK/NEUTRAL MODE ; 1 = NOT IN THIRD GEAR ; 2 = OVERDRIVE REQUEST ; 3 = EXCESSIVE POWER STEER PRES. , CLUTCH ANTICIPTE ; 4 = EGR DIAGNOSTIC SWITCH CLOSED ; 5 = TCC LOCKED ; 6 = FAN REQUEST BIT ; 7 = 0= A/C REQUEST ;--------------------------------- Equivalent $6E data: FDB $0038 ; 18. MCU STATUS FLG ; b0 1 = IN PARK/NEUTRAL ; b1 1 = NOT IN THIRD GEAR ; b2 1 = OVERDRIVE REQUEST ; b3 1 = EXCESSIVE POWER STEERING PRESSURE ; b4 1 = EGR DIAGNOSTIC SWITCH CLOSED ; b5 not used - OMITTED FROM S/W (1 = TCC LOCKED) ; b6 1 = FAN REQUEST BIT ; b7 0 = A/C REQUEST ;--------------------------------- Note: When I run a $6E bin in my 88, I see that bit 5 is always set when scanning. Scanning also interferes with the OD indicator, so it would need to be tested with and without scanning to confirm that the lamp and bit are related to each other. Need to find where bit 5 is set in $6E and prevent or force it to be cleared. Will look into later. Then you need to determine if there are any adverse effects. I've always wanted to get to the bottom of this issue, so I may test it myself, if I get around to it. |
