cjfrigo

2000 4.0 I have hooked up 3 obd scanners to it. Problem I'm having is it won't scan I know this is common but my buddies scanner says no communication ( crank sensor ground or voltage problem idk which ) but says the crank is working in safe mode .
My jeep runs fine reason its throwing a code is if it idles to long 5 min. Or less once warmed up . Will start to idle weird then the check engine light . I unhook my battery reset the ecm. Will run fine . Idk if I worded this right I'm using my phone sorry about grammer and spelling.

cjfrigo

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cjfrigo

ttt

Jesse Hallum

I disagree. I've never seen a scanner that did not work with any Jeep. I have a low-end Actron that is 15 years old that works fine with my 01 Sport. Make sure you're hooking it up properly and that the DLC and cable are not damaged.

I remember one guy who swore up and down that scanners didn't work on his Ford. I found out later that he never bothered to turn the ignition key on while performing diagnostics, so perhaps your procedures need review.

cjfrigo

I tried the first time at advance using there actron scanner . Went to my friends garage has a really good snap on scanner it said no communication and said about the crank in safe.I'm sure he knows how to use his scanner. Also tried a smaller one he owns still nothing. So three different scanners. No luck.

CCKen

If the freinds Snap On scanner won't communicate, how does he know the crankshaft position sensor is in "safe" mode [never heard of it]?

There are three modules that have SCI transmit capabilities (this is the circuit that the scanner uses to communicate with the CCD Bus), the PCM, TCM, and Controller Anti-Lock Brake module (CAB). The PCM also has SCI receive. If any of the SCI transmit crcuits are open or shorted, the scanner will show NO COMMUNICATION.

Attached is a schematic showing the DLC pinout and the various modules connected to the CCD Bus.

Not long ago a forum member had a "No Communication" situation and was getting concerned that he had an emssions test coming up and it was obvious he wasn't going to pass without a scanner. It was narrowed down to his CAB connection was bad. He disconnected the CAB and the ABS light relay and communication came back. He had his emssions test done. LOL

You should check each each pin cavity in the DLC for corrosion and cavities that have been expanded by someone shoving a meter probe in them.

If you had a scanner handy, you could disconnect your CAB (if you have one), or the TCM, and see if communication comes back. If it still doesn't come back, there may be a problem in the wiring from the DLC to the PCM.

cjfrigo

Well I ruled out that I do not have abs

cjfrigo

Or am i wrong ? Were is the cab module?

Jesse Hallum

Stating that a Jeep Cherokee that will not "scan" is "common" is without any merit whatsoever. Unless you can site an authority to back this up, your statement cannot be considered factual, PERIOD. I'm tired of people offering a misguided opinion as fact.

Jareduhhh

Check the connection to the computer under your driver seat.

CCKen

If you had anti-lock brakes it would be on the anti-lock brake hydraulic unit in the engine bay. However, I don't see a CAB Relay in your PDC so you probably don't have anti-lock brakes (empty relay socket, and it appears not to have pin cavities in the socket).

The only other modules with SCI Transmit would then be the PCM and the TCM.

Examine pin cavity 7 in the DLC closely (bright flashlight and magnifying glass) for corrosion or enlarged/distorted cavity. Corrosion may take on the appearance of gray or black, or if really bad, green.

If you did have a scanner/code reader handy, you could disconnect the TCM and see if "communication" comes back.

cjfrigo

Alright so I'm reopening this thread I have put this project aside to long know my jeep has some real bad problems and now I need the obd port to work so I started checking everything found out I have no clue what im doing with the multimeter I checked pin 16 with test light and on volts with the multimeter I believe there is power on pin 16 now I see that 4 and 5 are grounds I measured on ohms pin 4 to power on pin16 got like 63 ohms and then I tried five and got nothing I dont know if I'm doing anything right hoping you guys can help me out again

CCKen

What are you attempting to do? What do you want to achieve?

The test you did (highlighted bold in your post) really proves nothing, other than by the time you got to pin 16 (B+) to pin 5 you probably smoked you Ohmmeter.

cjfrigo

Still trying to get a scanner to work. I guess I am a noob but I was trying to see if 4and5 had resistance . I'm sorry I'm trying to use the info you gave me but idk what to do with it

Idk how to tell if any of the pins are either getting power, or if the grounds are grounded good. Or how to tell if any of them are receiving anything

CCKen

Print off this thread and take it to a shop, or your buddy's place with the scanner, and have him look into disconnecting the Transmission Control Module and see if "Communication" is restored. If it does restore, there's a fault in the TCM that has corrupted its SCI Transmit circuit.

Pin socket 7 on the DLC is the SCI Transmit circuit from the PCM and the TCM. Pin socket 6 on the DLC is the only SCI Receive circuit. It goes to PCM C3 pin C29.

If you had the skills, you could check the wiring from PCM connector C3, pin C29 to DLC pin 6 and from PCM C3 pin C27 to DLC pin 7 for being open. And those wires for short to ground.