OBD2 Diagnostic Plug Wiring

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Jan 23, 2008 | 08:20 PM

Trunknuts

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OBD2 Diagnostic Plug Wiring

I used a reworked harness for my LM7 (5.3L Tahoe engine) which did not come with a OBD2 diagnostic plug (under-dash plug). I purchased a plug with about 10" of wiring w/ it. Can anyone tell me how to wire it in. I looked in the manual but the schematic shows a "splice connector" between it and the PCM. Can the plug wires go straight to the PCM? And if so, what is the pin out? Thanks in advance for any help.

Jan 23, 2008 | 08:54 PM

cherryelky305

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my experience is with a camaro harness. however I believe that the general rule is that OBDII ports have 4 wires. two grounds, a constant 12V, and the data line. Wish i could help more, but i dont have my diagrams with me at the moment.

Jan 23, 2008 | 09:11 PM

jay_lt4

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pin 2 class 2 serial data
pin 4,5 ground
pin 16 12v+

Jan 24, 2008 | 04:48 AM

samdogmx

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here you go

Attached Thumbnails

OBD2 Diagnostic Plug Wiring-obd-ii_pinout.jpg

Nov 19, 2008 | 04:48 PM

wajouba

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Ok, I have a 240sx with an LS1 swap, and my car is very unstable... I really need to know what codes its firing up at me, but my OBD2 Connecter is not connected... my question is, where is the purple data line located?. do we take it from the original LS1 car dash harness? or is it in the ECU harness?

Thanks

Nov 19, 2008 | 05:05 PM

G-Body

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The purple serial data wire comes from the LS1 PCM. If you look at the diagrams in the FAQ sticky you should be able to determine which pin it goes to. If not, you need to tell us what year PCM and wiring harness you are using so that we can tell you where to look.

Nov 20, 2008 | 02:48 AM

wajouba

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how can I know whether my engine came from a 99 or 98 camaro? cause I saw the PCM pin outs before but didn't know which one to use... can you guide me on this?

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Nov 20, 2008 | 03:14 PM

wajouba

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whats an ect? :S pardon my dictionary of abbreviations

Nov 20, 2008 | 08:05 PM

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oange ss

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Engine Coolant Temp sensor, front sensor in the driver side head

Nov 20, 2008 | 08:18 PM

#11

wajouba

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it has 3, with the green that connects to the dash for reading of temp... but I heard 99s also have the 3 wired one... so what is mine 98 or 99?

Nov 20, 2008 | 08:54 PM

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oange ss

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only 98 has the 3 pin ECT sensor, 99+ coolant guages are PCM fed...so you have a 98 engine/harness

Dec 10, 2008 | 05:52 PM

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wajouba

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Alright, so I have a 98 harness and PCM, where is my serial data pin on the PCM?

Dec 10, 2008 | 06:24 PM

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oange ss

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C2 (blue connector) pin#58, purple wire

Dec 10, 2008 | 06:43 PM

#15

wajouba

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ok about the ground wires... both Chassis? or does one have to be from the ecu ground?

Dec 10, 2008 | 07:46 PM

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oange ss

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ALDL pin #4 chassis ground
pin #5 signal ground (ECU)

Dec 12, 2008 | 07:57 AM

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Speed Demon

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Quote:

Originally Posted by oange ss

ALDL pin #4 chassis ground
pin #5 signal ground (ECU)

What is the difference between a signal ground and chassis ground?

I know what a chassis ground is.

Dec 12, 2008 | 08:14 AM

#18

wajouba

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I have the same question in mind... so is a signal ground a ground comming from the ECU/PCM or comming directly from the negative of the battery? (which is actually chassis I think)...

Dec 12, 2008 | 08:26 AM

#19

Speed Demon

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Quote:

Originally Posted by wajouba

I have the same question in mind... so is a signal ground a ground comming from the ECU/PCM or comming directly from the negative of the battery? (which is actually chassis I think)...

I know on the BMW DME (PCM) it has serveral grounds that are switched ground/open by the PCM to control relays. I see in the F-body PCM pinouts that is has several grounds, are some of these switched (or signal) grounds?