no communication at OBD2 port

The title says it all, what could have happened to make the code reader not be able to 'see' the PCM?
I have other vehicles that this scanner can 'see' perfectly.
Scanner in question is an older "OTC System 4000".
A few weeks ago, this scanner worked with this car, any clues on what's up?
This car is known as "Riv 2", my second 1997 Riveria.

see if something is wrong with the obd2 port

albertj wrote:

see if something is wrong with the obd2 port

PT "Doctor, It hurts when I do this".
DR "Well, don't do that."

Two Rivs, no waiting wrote:

albertj wrote:

see if something is wrong with the obd2 port

PT "Doctor, It hurts when I do this".
DR "Well, don't do that."

Not quite...

For some reason the Riv's OBDII port is, well, kind of easy to damage.  So the first thing I'd do is check the wires near the connector to see if any may have broken inside the insulation, if any pins have slipped or bent, or if there's a short between pins. My guess is this isn't the case for you - but - it's easy to check and if you don't check (and fix) this first and it is a problem, all the protocol-adjusting you can possibly try won't work at all.

Second, the Riv only scans with scanners that will use the old SAE J1850 VPW (Variable Pulse Width Modulation). Many newer cars use newer protocols and some scanners don't connect well if at all to SAE J1850 unless you "ask" them to.  (by the way, Fords use SAE J1850 PWM (Pulse Width Modulation) communication patterns and Chrysler products as well as pretty much all European and most Asian imports use ISO 9141 circuitry). Bottom line is that nothing at all may be broken, just incompatible -- if your scanner has various protocol settings, after you check the wires just double-check your scanner's protocol settings. Scanners that can be used with "all OBDII" have to work with multiple protocols. For instance, for a quick scan I have Torque Lite on my phone and a bluetooth ELM327 dongle. When I go from checking the Riv to the Rendezvous, or one of my Volvos, and back it takes a while for the software to sense the correct protocol and sometimes I just have to go into settings and force it. For more detailed scans and capturing live data streams I have a dongle and software I got years ago from Alex Peper, "Car Code." (see http://www.obd-2.com/old.html). The dongle I got with that works great on the Riv and won't really work with *anything* else - it's no longer sold and probably has not been sold for a while.

Albertj

Just for reference for the rest of you:

On OBDII vehicles, you can usually tell which protocol is used by examining the OBD II connector:

J1850 VPW - The connector should have locations 2, 4, 5, and 16 wired, (and not location 10).
ISO 9141-2 and ISO 14230 KWP - Locations 4, 5, 7, 15, and 16 wired.
J1850 PWM - Locations 2, 4, 5, 10, and 16 wired.
CAN Bus - Locations 4, 5, 6, 14, and 16 wired.

The scanner systems built with ELM327, and STN's series of multiprotocol chips (see https://www.obdsol.com/solutions/chips/) usually figure things out for themselves when connected to the OBDII connector, based in part on which wires are "hot" but in my experience that does not always work as expected.

So check the simple and quick stuff first. Are there broken wires (there should not be) or bent or dislocated pins (those alone will fool your scanner) then is there a protocol problem you can fix via settings.