No communication with OBD 2 plug

[cp2295]

Hi everyone I’ve recently swapped a 96 4.0 engine/ecu/wiring into the 86 B2. Motor runs so i decided to get the obd 2 plug wired in. I’ve got the correct wires plugged into the ecu harness (purple, pink/blue, tan/orange) and I have 12v supplied to the orange wire, and the black, and black/white wires are grounded to the chassis. My obd2 scanner powers up but cannot connect. It says interface connected, attempts numerous protocols, and then gives up after it can’t find any that work.

There is 1 wire a light blue/white that I could not find where to hook up, but from what I’ve read it is for auxiliary items (abs, etc) so I don’t see it as a concern. But then again I’ve read it’s the J1850 bus+ wire which I see my scanner attempt to connect to that protocol. Wondering if that might be my issue. Another thing According to the diagram I found, the black/white wire should be signal ground and the black should be chassis ground. I cannot find anywhere in my engine control diagram where the black/white wire would go, only the pk/blu, ppl, and tan/org.

Any ideas? My scanner works fine in everything else I’ve used it on.


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[adsm08]

Assume the narrow side of the plug is the "bottom".

What is the resistance between the 3rd pins from the left, top and bottom.

What is the resistance between the 3rd pins from the right, top and bottom.

 

[RonD]

Found a 1996 OBD port wiring diagram

Pins are
((1 2 3 4 5 6 7 8))
(9 10 11 12 13 14 15 16)

1-8 being the wider part of connector

 

[cp2295]

Assume the narrow side of the plug is the "bottom".

What is the resistance between the 3rd pins from the left, top and bottom.

What is the resistance between the 3rd pins from the right, top and bottom.

There aren’t any pins in those slots. Only pins 2, 4, 5, 7, 10, 13 and 16 have pins.

I double checked continuity from the obd plug to the ecu terminals and they all check out good. Maybe I should grab the snap on scanner from work and see if it connects


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[cp2295]

Found a 1996 OBD port wiring diagram

Pins are
((1 2 3 4 5 6 7 8))
(9 10 11 12 13 14 15 16)

1-8 being the wider part of connector

Great diagram, I searched for about 45 minutes yesterday for something like this and couldn’t find nothing appreciate it!

Looks like that light blu/white wire goes to the GEM I wonder if I need a GEM for the obd plug to work...?


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[cp2295]

Yeah definitely starting to think that I need a GEM. Pulled one of the fuses for it on my 99 ranger that has the same pinout on the DLC and my scanner would not connect. Plugged the fuse back in and it connected no problem.

I should be able to get away with powering the GEM up (and grounding it) and then just connect that lt blu/white wire from it to the DLC plug, right?

Found a great diagram for the GEM on this link http://www.therangerstation.com/forums/showthread.php?t=170941 from you RonD.


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[adsm08]

What is the resistance from your one network line to the other one at the DLC. If it is not 60 ohms, give or take a few, your communications network won't work.

 

[cp2295]

What is the resistance from your one network line to the other one at the DLC. If it is not 60 ohms, give or take a few, your communications network won't work.

No continuity between data + and data - wires. There is continuity between a few other wires however nothing reading 60 ohms. The two pairs of pins that have continuity read 120, and 20 ohms.


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[adsm08]

The 120 ohm pair, there is your terminating resistor for the networked module. There are supposed to at least two modules on the network, which means two of those resistors, which is 60 ohms, rather than 120.

The network signal isn't super strong, it can get through 60 ohms of resistance, but not 120.

Also, double check that the two wires with 120 ohms resistance do run to the computer.

 

[cp2295]

Hey sorry for not replying been real busy lately. Anyways I went ahead and got a GEM from the junkyard and gave it power and ground and connected the light blue/white wire from it to the DLC plug for the hell of it. And of course it didn’t work, not sure if I got it all powered right or what voltage that light blue and white wire should have.

I tried a different (known good) PCM and i still cannot connect to the obd 2 plug.. are the resistors for the dlc in the PCM or along the wiring harness? at a loss here, real unfortunate too cuz the motor runs pretty bad and I can’t read engine data. And I would like to seat the rings before running it in the garage for too long!

On the bright side there are no leaks, I’ve got good oil pressure, and it doesn’t overheat!

Anyways anymore ideas are greatly appreciated.


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[RonD]

I can't see why you would need GEM or any other module connected to get PCM data
OBD2 readers are "universal" not all vehicles have GEM or other Body computers

Just the 3 wires from PCM, and 12v and Ground to power reader, reader does power up right?

PCM would also need power, does CEL come on with the key?

 

[cp2295]

I have not wired the CEL into the truck yet. However the truck does run (it’s an 86 b2 with a 96 ecu/wiring/motor). The pcm controls my fuel pump and all engine controls so I have to believe it’s working well enough to communicate a signal to a code reader.

I have a WiFi OBD 2 adapter that hooks to your phone, works flawlessly on anything else I hook it to. It gets powered up and sends a signal to my phone but once I try connecting it goes through a bunch of protocols and then fails to connect.

On another note I got the truck running great, found the coil pack was not grounded well, and I threw another spare coil pack I had laying around on there and it runs great now, so I’m stoked on that!


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[RonD]

If reader works on other vehicles then it is "universal", and it is powering up, the wireless adapter, then, in my opinion, its down to the connector, and the 3 wires between OBD connector and PCM

 

[cp2295]

If reader works on other vehicles then it is "universal", and it is powering up, the wireless adapter, then, in my opinion, its down to the connector, and the 3 wires between OBD connector and PCM

Gotta blame the connector then I guess. I got great continuity between the pcm and those 3 wires. Good grounds and good power to the plug. My only concern with the grounds is the “sensor” ground, which from what I’ve read shouldn’t be a problem that I have it grounded to the chassis, but you never know.


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[cp2295]

Anybody know what the voltages at each pin should be with the key on? (Beside pin 16)