OBD II will not communicate with computer

My "Maintenance Required" light came on, I figured it due to oil change interval, so I changed the oil but the light would not reset with the usual reset maneuver. I figured it would be a good time to pull codes, but I got a message from the code reader which told me the OBD port was unable to communicate with the computer. Tried doing this multiple times, as well as trying a second code reader.
I found no fuse problems, all the pins plug in properly, and there is no evidence that a pin "pushes out the back of the connector" when I plug in, so I'm a bit puzzled. It doesn't appear that there are others who have described this problem, so I'm rather curious now as well as stuck. I have previously had no issues on this vehicle in reading codes at all. Please share with me your thoughts.

2011 Tacoma MT Sport

 

Have you checked if you have power on pin 16 of the DLC and ground on pins 4 and 5?
If those are good you may try a different scanner, if that doesn't work it's probably gonna take an oscilloscope on the data lines to see what's goin on.

 

@Dm93 Nope, haven't. Didn't know what to check, but you know I will now and get back to you as soon as I can get to this in daylight. Thank you.

 

Okay, checked. Ground has continuity on pins 4, 5, and I have battery power on pin 16. I suppose the plot thickens now.

 

Do you have any other warning lights on besides the maint required?

 

Nope. That's the only light that is on.

 

Well, reading more into this, at least for the Maintenance required light: In 2011 the background in the gauges went from the orange gauge background to the white gauge background. Those with the Orange background use the Odometer to reset the Maintenance light, while those with the white gauge background must use trip A to reset this light. I have an 11 model. Apparently the ONLY thing which triggers the Maintenance required light is the odometer going 5000 miles since it was last reset.

This of course does nothing to address my inability to pull codes with my code reader.........willing to accept any insights into this.

 

OBD work today. I have read the fuse panels, and I suppose I can start pulling fuses and looking at them, but is there a specific fuse for this system anywhere that is the smoking gun fuse? "OBD" 7.5 amp fuse under the hood is fine, but others involved here? Seems it could save me time, and I don't have access to a way to interpret otherwise.

I have pulled down the harness to the OBD port so I have a little slack and access. All the pins appear intact, they don't push back out of the connector hub, and everything looks good here.

In checking those grounds in pins 4, 5 position. I put my DVM probe on the pin, and the other end on the Neg battery terminal, and got ZERO ohms which tells me it's continuity. Did I not do that part right somehow? Is there a better way to check for the grounds on pins 4, and 5 so that I am not heading off unhinged down the wrong pathway?

Appreciate input of course.

 

If you read Zero Ohms between the ground pins 4 and 5 and the negative battery terminal that is a good reading. If it were defective it would be reading very high or OL.

Read the DVM between pin 16 and terminals 4 and 5 and you should read battery voltage.

 

Yep, I've been getting battery voltage when I probe pin 16

 

I wish I had more assistance to give. I wish you the Best! Maybe @Dm93 will pick this back up with some help.

 

Random thoughts. Did you make sure your ODO was on the total miles setting when performing the reset?
I'd spray some contact cleaner in the OBD connector. Good that it appear so to be working now. I'm guessing no codes or you would have said as much.
Feels like two separate issue to me...?

 

Well, my "maintenance required" light, and my OBD disconnect are two separate issues. I solved the Maintenance light by putting the odometer on Trip A, as is required for my '11 MT DCSB Sport. Now that light has been shut off.

The OBD 2 issue is that I can not get it to link up to read for codes. I have no check engine light on, but was trying to read codes here, and my reader, as well as another reader, both good, will not connect. So at present, I'm trying to figure out why my code reader will not connect.

 

Measure the resistance between pins 6 and 14 with the battery disconnected, it should be 60 ohms.

If you have no other warning lights on I would have to conclude that the module to module communication is good and there's a problem between the DLC and the J9 junction connector.

 

Cool on the light reset. Did not know 2011 procedure used Trip A. Highly recommend cleaning the heck out of both the OBD2 and OBD reader connectors before troubleshooting further.

 

Okay, probed 6-14 w battery disconnected: 62 Ohms

Don't know if this is a good thing, or just leads us nowhere..........

 

Will your code reader work in another vehicle?

 

Yes, code reader works in other vehicles. Thanks for asking.

 

1. What code reader are you using; and

2. Does it automatically select the comms protocol, does it try all of them, or can you manually select the one you want to use?

 

That suggests that the CAN lines are intact at least to the terminating resistors, not really much more you can do at this point without scoping the CAN lines or trying a different scan tool.
I would be curious if you could talk to the other modules but I'm asuming you just have a basic scanner that can only read PCM codes?