Using an entire dash harness from a '90 into the '87: PROS: Everything in the dash should work properly. The C100 connector is similar CONS: A few pins from the existing ECM will need to be spliced over to the new cluster. VSS sensor should probably go direct to B10 and B9 on the ECM, and then the 4000PPM output on B11 will need to be spliced into E2 on the CCM. Not sure if splicing the ALDL into the ECM is a great idea. Probably not. The FUEL PUMP circuit may need to be moved. Maybe not. I think it is hot at all times on the '87, and the ECM switches the relay. On the '90 I think the circuit is energized from the DERM. The fuel pump power comes from the fuse box in the dash, so at minimum the circuit will probably need to be directly spliced from the fuse box direct to the body connector.. maybe. Cooling fan on B7 might need to be altered / run direct to ECM. The headlamp circuit may or may not be compatible. more investigation needed. Dash swap issues: 1) 90+ Headlamp switch won't drive <88 head lamps (3-relay style) > Convert headlamps to module style OR retrofit earlier switch to dash. > But why? The schematics look the same. Needs more data.. 2) CCM is required to drive LCD on '90+ dash, LCD operates speedo + fuel gauge CCM needs to be used with either '90 harness, or spliced to older harness as indicated below. 4) CCM comms with ECM, will flash 'sys' if no ECM avail > Remove 'sys' lamp from DIC panel 5) Power window switches moved from console to doors > Need to either use whole '90 interior harness or '90+ Door harness must be spliced into doors, along > with mirrors 6) Wiper switch moved from door to column directional wand > Original switch must be mounted, or circuit rewired to fbody switch in column 7) HVAC wiring is not compatible between years > If using the entire '90 wiring, this is not an issue. (But CCM programming will be needed) > or maybe Maybe '90+ manual HVAC controls? Blower motor should be the same. VSS ISSUES: ZF6 Speedo is 4000 PPM CCM Requires 4K PPM VSS on pin E2 '730 ECM will send a 2000PPM signal to cluster on pin C1 '730 ECM will send a 4000PPM signal to cluster on pin B11 '730 ECM VSS input HI (yellow) on pin B10 '730 ECM VSS input LO (purple) on pin B9 '730 C6 is buffeed VSS input (from 165 swap) For '165 or buffered '730/'749 applications, use speed buffer box. Buffer will produce both 2000PPM to '165 ECM and 4000PPM to cluster. Buffer wiring: Purple and Yellow wires go to VSS Pink w/ black stripe to POWER Brown to ECM Green with Black stripe to CCM Black with white strip to GROUND IF not using a complete '90 dash harness, and splicing original '87 harness the following will need to be spliced to the CCM: CCM related splicing: At a minium the following will probably need to be hooked up: F1 Needs to go to battery (LCD fuse) F2 splices to F1 to battery C1 to Ground E16 to Ground E4 To go to switched ignition (wake up, run) E5 To go to switched ignition (run, start) C11 not really needed, but could go to 'key in' D15 could go to door switch, not needed C4 could go to unlock C5 could go to unlock C12 LH door open (not needed) D16 RH door open (not needed) E12 and F5 will need a resistor to mimick VATS E2 will need a 4000 PPM signal from a 4-out buffer or ECM For VATS ECM cars, D3 can go to the ECM F16, F11, F14, F13, D1, E1, D11 All go to LCD on Cluster E11, E10, E15 can go to the DIC switch panel, but I doubt it will do anything Things that might not work properly if a '90 harness is not used: LCD probably will not dim/illuminate properly without '90+ headlamp switch All the MPG and range data probably will not work since the ECM will NOT be online in the data stream. Other electrical issues: Doors will need power switches re-routed and spliced. Should be tested while dash is out prior to installing new dash.
Mounting issues: "L" shaped brackets will need to be made to mount top of dash to car HVAC plumbing will need modifications