96 GTS ISO 9141 2 K line L line Diagnosis quot PCM is not supporting Communications quot

[MrCreosote]

DRB III failing to communicate with PCM.

What I've learned so far:

• K-line logic Hi/Lo is Vbat/0
• K-line Measures Vbat w/DLC breakout box and NO scan tool connected.
• L-line Measures 5v w/box & NO scan tool
• Some communication must be initiated to see K-line logic stream - a connected scan tool can do this.

Have found no English postings about L-line - a few Spanish ones but nothing in English.

QUESTIONS:

Is L-line used?
IF YES:

• What is Vhi/Vlo?
• Is it a different data stream or a "mirror" of K-line?
• IF DIFFERENT: must communication be initiated to see logic stream?

I did notice that my battery was 11.3v and K-line was also 11.3v: If K-line is supposed to be 12v Hi and I only have 11.3v, could this be why my DRBIII is not initiating communcations? (But then it doesn't with engine running either.)

NOTE: After days of "The PCM is not supporting Scan Tool Communications" I got my BOB (Break Out Box) and found it extremely tight to connect. I then connected my DRB to the BOB and actually got to the "ENGINE" module selection which then failed to communicate. All subsequent connects failed with the "The PCM is not..."

[99RT10]

Do you think the Batt voltage might be the problem?

[MrCreosote]

I'm just guessing.
If the design is robust, then NO, battery voltage should not be a problem.

There is a Communications Diagnosis Manual referenced in the "Guide to DRBIII" manual that I cannot find for any 1996 Dodge model.

There doesn't seem to be much information on the DLC in either the FSM or the PowerTrain Diagnosis Manuals. Perhaps the Body Diagnosis Manual? (which I don't have.)

The Full Wiring Diagram does not appear to be in the FSM either. I know Ford had a rather thick Wiring Diagram Manual for my 2000 Windstar that had the full diagram and all the sub-systems with connector pin outs and locations.

Mitchel didn't have any info on the DLC pin callouts either.

It's going to be a long process to acquire the necessary information to diagnose the failure to communicate for this ISO9141 K-line system. If it was CAN, there is tons of into out there.

[MrCreosote]

NEXT DAY PROGRESS:

Have DRB hooked for K and L split screen through DRB Break Out Box - NO SCAN TOOL CONNECTED.

Now, CANNOT GET ANY VOLTAGE out of K and L with Key On or Running. yesterday got Vbat and 5v respectively.

All I get is noise band from 0 to 2v approximately.

QUESTION: Should I see Vbat on K-line just with Key ON? (Running is a problem in the garage I'm in - especially with car running so rich.)

ALSO ran DRB as Generic Scan Tool and was able to get 32 parameters such as IAT ECT RPM etc.

[MrCreosote]

UPDATE: Why no Communications Diagnosis Manuals: The Guide to DRB III was published 1995 which is Pre-OBDII.

But I did find a detailed description of the K&L Line initializations in the following White Paper:
Implementation and Validation of K Line (ISO 9141) Protocol for Diagnostic Application

[MrCreosote]

After a few days trying to view logic train and debug, with battery on charger and at 14.5v, the DRB mysteriously started communicating using the year specific diagnostics (1994 thru 1997 and not Generic.)

The Logic Hi/Lo voltages I saw were unlike ANY of the ISO 9141-2 Vbat and 0 spec I read everywhere. The only time Vbat/0 are present is at the beginning of the "handshake." After that it's all 5v/0 for year specific. Generic is totally weird with what looks like a Vbat/0 trigger with 4v/2v/0 packets.