No Communication Scan Tool Diagnosis
Throughout my various positions either in sales, business development or training, the topic of "no communication with my scan tool" has come up frequently. Last week, while attending the Autologic National Training Conference in Orlando, this was a popular question from those stopping by the DrewTech booth. The question is normally followed with the statement "and I tried several tools and still no communication". That is clue something else is going on! It also now is more relevant as we see most manufacturers offering ECU programming via J2534.
I am going to publish a 6 part series here on DN on how to properly diagnose the most common vehicle networks. You will need a decent Digital Storage Oscilloscope (DSO), a DLC breakout box, an OEM network wiring diagram, and your scan tool (OE tool is preferred, since theoretically we know that works correctly & most have networks tests incoporated). This will not be an overly technical dive into how they share data but a quick reference in how to set up your scope, scan tool and quickly test the network integrity.
I will publish each of the installments as separate posts, linked from here as well, so you can easily digest the one you need help on when the vehicle is in your service bay. I chose the common protocols that are on the J2534-2 list so you will be able to use the info to cross manufacturers when necessary. Nine of the sixteen DLC pin assignments are mandatory cavities (assuming the OEM does not deviate, which happens occasionally), so once you learn and know the pin locations, you can quickly identify what busses are wired up to the DLC.
The Networks covered will be:
- SAE J1850VPW- DLC pin 2
- SAE J1850PWM- DLC pins 2/10
- ISO 9141-2 (K-Line, L-Line) DLC pins 7/15
- ISO 15765-4 (Dual wire, HS CAN) DLC pins 6/14
- Single Wire CAN (normally DLC pin 1)
- SAE J2610 (SCI) (sprayed all over the place!)
DLC pins 4/5 are always grounds, DLC pin 16 is always battery power.
Hi Bob, Off topic, when did you start the new gig, and Congratulations!
Hey Mike. Started with DT/AL/OPUS IVS in the middle of May. Great group of guys in these companies and a very forward thinking team approach to problem solving.
J1850VPW has been posted and a link added above. Any questions, post them in the thread itself so they stay associated with that protocol.
Good series on scantool and network communications Bob!
As far as SWC goes I have only seen it applied with GM pin 1 as you mentioned I’ve seen manufacturer specific use of other “manufacturer discretion“ pins that are similar in functionality but they don’t necessarily meet can communication protocol. I like doing network diagnostics on GM as the different can channels make it easier to rule out the usual suspects
Bob - as always, feel free to ping me if any specific tough comm issues come up... ...also, for K-line stuff, I think that this stuff is still relevant for those working on older vehicles:
Cheers and Happy Holidays!