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OBD 1.5 to OBD 1


GM Guy

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Hey guys and Happy Holidays! My 95 GP w the 3100 and OBD 1.5 is getting a bit long in the tooth after 277k and was looking to find out if anyone has done a backwards swap to OBD 1 lq1 and problems. Would be using my 91 Z. My GP doesn't appear to have a pressure sensor which is used for idle on the lq1. Also does the swap affect the anti theft and key/chip?

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95s were obd1, not obd1.5. You need to get c100 color codes as they tended to change a bit. If they are diff, theyre not hard to modify. Took me ten minutes on mine including wrapping my whole harness in electric tape. Good luck :)

Hey guys and Happy Holidays! My 95 GP w the 3100 and OBD 1.5 is getting a bit long in the tooth after 277k and was looking to find out if anyone has done a backwards swap to OBD 1 lq1 and problems. Would be using my 91 Z. My GP doesn't appear to have a pressure sensor which is used for idle on the lq1. Also does the swap affect the anti theft and key/chip?
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i more or less did this exact swap in..... 2009?

 

there are a few ways to go about it, from making an adapter harness at the PCM connectors to swapping the entire underhood harness.

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x2. by definition there is no 'obd1.5' but 94-95 cars have been dubbed that due to their 'special' needs lets call it :lol:

 

But Saar made me an adapter harness by the PCM. Been working great since day 1. How many yrs ago was that! :lol:

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depends on what you qualify as 1 vs 1.5. a lot of 94-95 cars randomly got the 16 vs 12 pin connector, you could have two otherwise identical cars/PCMs, just the different connector, so i can't recommend that being used as a determining factor.

 

94-95 LQ1(and A-body L82) used OBD2-style DTC descriptions, but the PCMs themselves were little more than slightly modified 93-earlier 3800 PCMs.

93-95 L82 used OBD1-style DTC descritions, but the PCMs were fairly unique, sharing a lot of design similarity to the 94-95 LT1 and 93-95 Northstar units. also used a pair of flash PROMs.

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depends on what you qualify as 1 vs 1.5. a lot of 94-95 cars randomly got the 16 vs 12 pin connector, you could have two otherwise identical cars/PCMs, just the different connector, so i can't recommend that being used as a determining factor.

 

94-95 LQ1(and A-body L82) used OBD2-style DTC descriptions, but the PCMs themselves were little more than slightly modified 93-earlier 3800 PCMs.

93-95 L82 used OBD1-style DTC descritions, but the PCMs were fairly unique, sharing a lot of design similarity to the 94-95 LT1 and 93-95 Northstar units. also used a pair of flash PROMs.

 

While on that subject, what scanner would you use on a 94-95 LQ1 car? I know the paper clip trick doesn't work on it, so which scanner will work on these cars? Would it be the same as the LT1 Camaro's plug?

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I use an ancient Actron CP-9110 on my '95 LQ1, it seems to work well..but you'll need a GM cartridge, and cable, which may or may not come with the scanner. I lucked out, and mine did. Paid $80.00, I think on Ebay for it several years ago.

 

EDIT: There's one on Ebay right now, but it has a Chrysler cartridge, so you'd need to buy a GM cartridge with the GM ALDL cable to make it work on your LQ1.

 

http://www.ebay.com/itm/Actron-111-Diagnostic-Tool-ScanTool-Model-CP9110-w-Chrysler-Software-Cartridge-/181264522317?pt=Motors_Automotive_Tools&hash=item2a34351c4d

Edited by Galaxie500XL
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Personally id convert everything i get to obd2 if i can. I view obd1 like a benign brain tumor, sure you can live with it but its still a damn headache. You never hear of people having trouble scanning obd2. Just my $0.02. :)

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I use an ancient Actron CP-9110 on my '95 LQ1, it seems to work well..but you'll need a GM cartridge, and cable, which may or may not come with the scanner. I lucked out, and mine did. Paid $80.00, I think on Ebay for it several years ago.

 

EDIT: There's one on Ebay right now, but it has a Chrysler cartridge, so you'd need to buy a GM cartridge with the GM ALDL cable to make it work on your LQ1.

 

http://www.ebay.com/itm/Actron-111-Diagnostic-Tool-ScanTool-Model-CP9110-w-Chrysler-Software-Cartridge-/181264522317?pt=Motors_Automotive_Tools&hash=item2a34351c4d

 

I've seen that floating around for a while, but I haven't seen the Cartridge for GM come up.

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IIRC, the Actron part number for the GM cartridge is CP9111. A new one will have both the cartridge, and the cable...you'll need both.

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My 95 with the 3100 is definitely the 1.5 and hasn't changed magically since we got it new. No one around here has the scanner/cable to hook it up and the part store guys used to look at me strange when the 1 or 2 wouldn't fit after I repeatedly told them. No doubt special needs. Also it was hit/miss across the GM lineup for late 1994, most 95s got 1.5 unless they still had parts on the shelf. Big upside to 1/1.5 is no MAF to go bad. Downsides are obvious.

Edited by GM Guy
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with any 94-95 W-body, you'll either have a 12 pin(like everything else GM OBD1 from ~1984-upwards) or 16 pin OBD2 connector. the PCM communicates using the OBD1 8192 baud protocol, so any scanner that reads actual serial data and not just flash the SES should work.

 

i see no real downside to the OBD1 PCMs, especially once you start writing custom code that surpasses the capabilities of most common OBD2 PCMs.

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Personally id convert everything i get to obd2 if i can. I view obd1 like a benign brain tumor, sure you can live with it but its still a damn headache. You never hear of people having trouble scanning obd2. Just my $0.02. :)

 

I agree, such a PITA to troubleshoot. Maybe yet another L67 swap on the horizon? lol

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