the ground pins on your OBD connector. They must tie to body ground somewhere.

 

Appreciate the quick response. I'll trace the ground later this afternoon.

 

Finally had a chance to do this. Tracing the ground was a real PITA, so I spliced off the wire and connected it to a new ground, one to the chassis and one to the body. Both locations had less then 1Ω of resistance. But the problem still persists; my little handheld scanner can't connect but a buddy's Snap-On scanner is able to.

Any thoughts or other areas which I can troubleshoot?

 

Just bringing this to the top and hoping someone has an idea / possible solution.

V/R,

Chevy_Scout

 

Have you checked your fuses? We had similar problem this week on a 2005 Cadillac Escalade and my mechanic right away said we had a blown fues. The fues was replaced and problem solved. Just a thought in case you haven't done so already.

 

This is definitely a unique/interesting problem.

I can tell you for sure that different scan tools will have different ways of communicating with the vehicle, and that can affect operation.

Most handheld scanners (code readers) will draw power and ground directly from the OBD port (Pins 16 & 4/5). A bad ground or low voltage at the OBD port will prevent them from powering up.

Most larger scanners (dealer/pro level) will utilize pins 16/4/5 in different ways - if it’s got a cord connection to the scanner, those pins are usually just an input for the device to recognize its connected to the vehicle, but the scanner itself uses an internal battery. If the scanner uses a Bluetooth transmitter to connect, the transmitter gets power and ground from the OBD port.

Your previous posts state you repaired the ground circuits and are reading battery voltage at pin 16, but if you try to power a test light from pin 16 (ground light at battery or chassis) will it light? If not, there’s high resistance in the circuit and it needs to be repaired or a new wire run from a fused battery circuit (pin 16 gets its power from one of the power port/lighter circuits).

One test to verify the communication circuit is in tact is to disconnect the battery, then check resistance between pins 6 & 14 - these are the high speed comm circuits - it should read 60 ohms. If it reads open/OL or 120 ohms, there’s an open in the communication network and further diag is required.

Are there any OBD devices installed on the vehicle? If you’re not sure, can you post a pic of the port?

 

This was the first thing I checked.

 

Thanks for the detailed explanation; I'll check the pins, per your instructions, and post the results here. I'll also post a picture of the port.

V/R,

Chevy_Scout

 

Finally got around to testing this out.

Pin 16 powers a test light just fine, not problem there. Tested the resistance of Pins 6 / 14, and it's reading about 60Ω.

Are there any other area's I can troubleshoot? A buddy of mine suggested getting a new ECM, but I'm not sure if that'll solve the problem.

V/R,

Chevy_Scout

 

It is highly unlikely that the ECM is to blame for this issue.

Based on everything I’ve read so far, I think the blame lies with the shop’s scan tool and/or operator.

Are there any other shops you can go to for smog inspection? Even if it’s out of the way, it may be worth going to another shop if their scanner connects to the vehicle.

And are there any aftermarket devices connected to the OBD port?

I’ll post more later after I’ve had a chance to review info specific to your vehicle - all I’ve told you so far is basic troubleshooting.