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Discussion Starter · #1 ·
I've posted on another forum and have received great info (thanks mukluk) but I have not resolved my issue. I figured I'd post here to see if anyone else has any answers. 1998 Wrangler Sport, 4.0, Manual Tranny.

Symptom: No Link to the PCM from my DataLink (OBD2) port. I have a "Check Engine" light. The Jeep starts and runs fine. I need to get a link to the PCM to figure out the CEL and eventually get this inspected. I need the link for NY state inspection.

Things I've done:

1. Checked continuity on both send and receive (SCI) wires from port to PCM with good results.
2. Checked to see if SCI wires were shorted to ground. No shorts to ground
3. Checked to see if SCI wires were shorted to each other. No shorts to each other.
4. Wires 4 & 5 on DataPort are grounded properly - Tested
5. I get the following voltages at the DataPort:

Wire 3 (CCD BUS (+))= 2.48V
Wire 4 (Ground) = 0V
Wire 5 (Ground) = 0V
Wire 6 (SCI Receive) = 4.78V
Wire 7 (SCI Transmit)= .01V
Wire 11(CCD BUS (-))= 2.48V
Wire 16 Power = 12.46V

6. I took the DataPort apart and put the wires directly on my OBD2 Scanner with same results. (BTW OBD2 Scanner works on my 2003 Jeep Wrangler, 2012 Ram, & 2017 Hyundai Tuscon).

7. I have replaced the PCM with a refurbished one from Flagship One. Same results

8. I have wired directly to the back of the PCM connector with a stiff wire and then to the OBD2 scanner on both PCMs with same results.

9. I have removed sensors, one at a time, and check both PCMs with the scanner. No Link

I am at my wits end.
 

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Discussion Starter · #3 ·
What kind of scanner are you using? Have you tried a different scanner?
I've tried two different scanners. One is an Actron CP9125 and the other was my buddy's. Not sure but it wasn't an Actron it was a different manufacturer. I think it may have been an Ancel.
 

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I've tried two different scanners. One is an Actron CP9125 and the other was my buddy's. Not sure but it wasn't an Actron it was a different manufacturer. I think it may have been an Ancel.
I assume both couldn’t connect. Wanted to rule out a bad scanner.

How did you test power and ground on the obd2 connector. Did you use a VOM or a test light? Concerned if those appear to be good grounds and power but they can’t carry enough current to power scan tool.
 

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Discussion Starter · #5 · (Edited)
I assume both couldn’t connect. Wanted to rule out a bad scanner.

How did you test power and ground on the obd2 connector. Did you use a VOM or a test light? Concerned if those appear to be good grounds and power but they can’t carry enough current to power scan tool.
Yes. Neither connected.

Regarding testing, I used a Volt Meter. I also ran short stiff wires to the back of the connector as it was connected to the PCM at pin 27 & 29 and put them directly to the scanner as well as a power wire and a ground and still got No Link on both PCMs.

I can only think that there is a short somewhere else other than the lines on the DataPort that is not enabling me to link to the PCM.
 

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What I am saying is using a test light, test the ground and power from the OBD2 connector. This ensures the wire can pass enough current. It's possible for a wire to pass a continuity test but not carry enough current.

Another thing to try is unplugging the connectors at the PCM and check for a)pins in the plug being spread or not making contact, b) any bent pins on the PCM.
 

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Discussion Starter · #7 ·
What I am saying is using a test light, test the ground and power from the OBD2 connector. This ensures the wire can pass enough current. It's possible for a wire to pass a continuity test but not carry enough current.

Another thing to try is unplugging the connectors at the PCM and check for a)pins in the plug being spread or not making contact, b) any bent pins on the PCM.
I Ohm'd out the wire. I set my Meter to 200ohms (smallest setting) and it read 00.6 and then checked the wire alone to check the circuit and it read 00.5 so subtracting that out of the equation, my ohms are low.

I have checked the pins on the PCM it seems like a hundred times.
 

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Discussion Starter · #8 ·
After playing around with a few different scanners, I got tired and went to Autozone to see if they could scan it. Lo and behold, they were able to scan it. It did take forever though and the salesperson even said that he's only seen it take that long once before.

I got the code and it was a bad TPS. I put a new one in and within the 3rd start, the check engine light went away and it's running well.

However, it still doesn't answer why other scanners don't link. Perhaps they give up too soon. I just hope when I need to get it inspected, the link to Albany DMV doesn't time out and fail the Jeep.
 

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I Ohm'd out the wire. I set my Meter to 200ohms (smallest setting) and it read 00.6 and then checked the wire alone to check the circuit and it read 00.5 so subtracting that out of the equation, my ohms are low.
It sounds like you found the problem but as described above, an Ohmmeter can show a perfect/great connection yet the connection can't pass enough power (amperes) to make the circuit work.

Case in point, I had an old BMW and the brake lights weren't working. I got out my multimeter and with the bulb out, I measured 12 volts to the brake light bulb connector when the brake pedal was stepped on. Should work, right? Nope it didn't. I ohmed it out and the ohmmeter showed a great connection from the brake pedal switch to the bulb housing. The ground was fine too. Very baffling, especially for a guy troubleshooting extremely complex electronic gizmos like transmitters, receivers, amplifiers, etc.

The problem turned out that one of the push-on brake light connectors had been crimped too hard and all but one strand of the stranded wire had been cut leaving just one tiny uncut strand connecting the light socket to the brake switch. Enough for the volt meter to see 12 volts at the bulb socket and enough for the ohmmeter to see a good connection since neither of those require much current to flow through that single strand. But put the entire load of the bright brake lights on that single strand, it couldn't carry the current so the bulbs wouldn't work.

Being able to measure the correct volts and a good connection won't always tell you the connection and/or wiring is good. :)
 
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