Downgrading computer, and the year differences

[Gemmer]

I?m planning on downgrading my computer and wiring system from a 94-95 system to an earlyer tunable, manual friendly, system.

I?m wondering what changes were made to the LQ1 over the years. (I remember a page on 60degreev6, but I cant seem to find it) I assume I can use any harness and computer from a 91-93 without too much problem?

Also, do I have to downgrade my plenum or can I simply install a MAP sensor to the 94-95 one. (I haven?t seen how the MAP attaches to an earlier plenum)

[patgizz]

you can just install the earlier MAP bracket and sensor (which i think i might have). i used a 94 3.1 harness on mine to retain my stock newer fuse blocks and relay centers, and my engine/trans is a 91.

in 94 they got the cam sensor and some kinda crank sensor or something behind the balancer, and went from speed density to maf.

[jmgtp]

Re: Downgrading computer, and the year differences

Also, do I have to downgrade my plenum or can I simply install a MAP sensor to the 94-95 one. (I haven?t seen how the MAP attaches to an earlier plenum)

You can install a MAP sensor. If you look at the rear passenger side of you plenum you will see a plastic block with some vacumn lines in it. The 91-93 dohc cars used a slightly different block which had accomodations for the map sensor to snap into it. The plenums from 91-95 are the same, you will need to attain the older style plastic vacumn block (I have no idea what this piece is called, and neither does GM as my service manual I recall used a different name for it than the GM parts manual). Mine shattered when I dropped it and the dealer was the cheapest place I could find one, I believe it was $17 for that piece.

[Gemmer]

Hmm, so with a pre 94 DOHC harness Ide have to use the older style fuse block?

(not sure on the differences since ive never peered into a pre94 bay)

[Gemmer]

heres another Q, does the pre 94 ALDL setup differ from the 94+?

[dohcfiend]

also there are some slight differences in the vacuum hose configurations i think. the engines have different pcv valves. and the 02 sensors are different 91-93 use 1 wire 02 sensor and 94-95 use 4 wire 02 sensor. where are u at gemmer? i can get you a harness and computer for a 93. i can get the pcm very quick, but the harness would take time. would you consider trading pcm for pcm and harness for harness?

[Gemmer]

Bump



So no one knows about the ALDL plug? Like, lets say I swapped the 94 engine harness, all of the sensors, ECM, all that jazz with that of a 93...now I'de be running a MAP based management system...but would I be able to scan the computer or would I still have the gay 94-95's inability to scan.

[Juglenaut]

Wire color varies...Please read last paragraph, I am not certain of placement.

91-93 uses a WHT/BLK and a ORG lead for the data link.>> I think the ORG lead is the diagonostic link and WHT/Black is serial data not sure

94-95 uses a single TAN lead>>Depending on class TAN lead can either be Serial class 1 or 2 also has a closed lead called Output/field service enable. I don't think a manual default code readout is system enabled. Requires a OBD-II equiv to scan.

What I would do is swap to the ALDL connector, when you get a new harness, or find the colors on the DLC connector match up the leads from the new harness>>> make pins on the DLC=ALDL: #7 = A, #5=B, #2=D, #10=E, #15=M...Meaning which you take your A lead and terminate it to pin #7 lead and so on....Take your B terminate it to pin #5...

These pins are based on a Auto Xray scanner connector pin used and labled as such, and Wire DLC and ALDL data ports...

Hmmm a thought>>> the pin selections may have different placement going into the scanner>>>Let me run a continuity test to verify pin placement to the scanner

[Gemmer]

Great info

[Juglenaut]

Debugged error

Can't delete....

[Juglenaut]

If you transfered to ALDL you would need an ALDL connector for most scanners to read....

There arn't enough pins to match up to the pin location going into a scanner between DLC and ALDL.

It is that field service enable that keeps people from doing a default disgnosis on DLC...All the manuals I have read say a scanner is required for DLC.