OBDII not communicating with Scan tool

I took my truck to the dealership last week to get the Clock Spring recall done. The tech called me a few hours later and told me they were not able to communicate with the ECU. He said they tried a couple different Scanners to rule out a faulty Scan tool but they still weren't able to get it to communicate.

The guy said his mechanic said he could fix the problem for $200. I said no thank you believing that for the dealership to charge only $200, it must be something fairly simple to do. I did not ask what was wrong thinking he wouldn't tell me. I have gone and checked all the fuses already and everything seems fine.

Is there a diagram of the OBDII connector for an 07 prerunner showing what wires should have power, etc? I want to try and fix it myself instead of paying them for something that is possibly really simple. Any ideas? I have a multi-meter and hope that could help me figure this out.

UPDATE:
I took my truck to a different dealership and dropped it off for the recall work. I get a call later from the service adviser saying they weren't able to perform the recall. They would need 3 hours to diagnose the problem before they could proceed - I declined again. When I picked it up, I spoke to a different adviser as the one I was assigned was not around. This other very helpful adviser looked at the notes from the tech and told me they were able to perform the spiral cable recall, as well as trimming the accelerator.

They were NOT able to re-flash my ECU though. I asked why that was and he told me: "I'll give you the technical answer." He said it has to do with ohms and amps. He said that the tech noted that there are a bunch of aftermarket wires in the dash. The adviser said that there must be an aftermarket wire getting power from a power wire that runs to or from the ECU. They will not perform a re-flash until the amperage/ohms read from the OBDII are what they should be. They don't want to try to re-flash only to have it crash midway and mess up the ECU because of some aftermarket wire feeding power from the ECU cable. He then told me: "The only reason I know that is because I know what he's (the tech) talking about." He asked me what kind of aftermarket things I have wired and I told him the only things in the dash are:
- Aftermarket stereo
- All new Aftermarket speaker wires from back of stereo to 4 channel amp. Then speaker wire to each speaker.
-Power wire & signal wire to powered subwoofer

He said that one of those items must be getting power from a wire that corresponds to the ECU. His suggestion was to simply unplug all of those accessories so that they aren't pulling any power from the ECU cable system. That way the amperage & ohm rating should be back to normal and they should be able to perform the recall.

Does this make sense to anybody? I know there are some Toyota Tech guys on this site. Hopefully they can chime in.

One other thing of interest; the tech noted that the check engine light is on. It's not on in the dashboard and when I had smog done, it wasn't on either.
The light works since it lights up on start up, but it doesn't stay on indicating that the engine needs to be checked. Wonder if he confused the "Maint Rqrd" light for the check engine light??

 

go to autozone and see if they can scan it. it has to be a can capable scanner of course

 

The OBD2 port is usually fused. Check all your fuses.

http://www.customtacos.com/forum/showpost.php?p=1801939&postcount=4

 

Bump.
Anybody have any other suggestions on how to diagnose & fix this issue myself?

I checked all the fuses under the hood as well as under the dash and they all seem perfectly fine.

 

does the yellow wire in the DLC connector have power

 

I don't know but I will check this afternoon.

 

UPDATE:
I finally took my truck to a couple of electricians to figure out what was up with my OBDII port.

1st: neighborhood mechanic (who also has a Tacoma) said his scanner could not communicate with the computer.

2nd: 2 weeks later, General mechanic with a shop said his scanner was unable to communicate with the computer.

3rd: Same day as general mechanic, Auto Electrician with shop WAS able to get his scanner to communicate with my trucks computer. It showed no errors and that everything was fine. Tried it several times and it worked fine.

4th: Since the last guy told me it was working fine, about 5 days later I went to get my smog check done. Their scanner was successfully able to communicate and confirm no codes in my trucks computer & passed the smog check.

1 week after smog check, I drop my truck off at the Toyota dealership to get the two recalls done... and guess what? I get a call about 3 hours later saying their computers/scanners (3 of them) were not able to communicate with the truck's computer and so they cannot do any of the work until that's fixed. I told them an electrician was able to get his scanner to read it and so did the smog place and they just said they didn't know why but they couldn't do anything because their system wouldn't read it.

I'm completely fed up! I have no idea what to do. The dealership wants to charge me $500 now to "fix" the problem. I'm going to take it to the electrician again and see if his scanner will read my truck's computer still. I'm going to try a different dealership if his scanner works fine.

Any ideas what the hell could be going on? The only thing I can think of is that possibly one of the prongs/wires in the adapter has bad contact and thus with vibration and/or movement of the adapter the contact is lost.

 

Thanks, I'll print that out and test it out this weekend. Otherwise, I'm going to take it to the electrician again.

 

How'd this work out Rocco? Good thing you got other opinions. When you got smog cert they actually connect to the OBD and looked for fault codes? Just went through that and don't recall seeing that? Barely want those yahoo's opening the hood on my vehicles let alone anything else. Biggest rip-off ever but that's a whole nuther story!

 

Yes, the smog place brought out their scanner, hooked it up to the OBDII port and scanned for I'm assuming fault codes and/or maybe specifically for a check engine fault code that would automatically fail my truck's smog test.

 

No experience here, but from what you've posted I would suspect that the "helpful" tech had your answer. The Toyota scanners check for proper volatage/resistance prior to flashing the ECU. The other scanners, from the emissions station and your mech friend, are not checking for voltage/resistance but rather just pulling the codes which does not require the checks that an ECU flash should.

 

Did you ever figure this out? Its been 10 years lol
Mine is doing this now.

 

I'm in the same boat. 2006 Tacoma took in for smog test and after 30 mins the tech told he could not establish communication with my OBD system. Checked OBD fuse and good. Plugged in my own scanners and home and they are powering up but not able to establish comms.

checked back shell of OBD connector and no loose or pulled wires.

I suppose after 18 years it could be the ECU, but hoping to hear back from someone

 

Are you experiencing any other problems with the truck?
If so, what are they?

We need to know all we can to help steer you in the right direction.

 

No other issues with truck. Just took it in for smog check and was told they could not connect to OBD. Checked OBD fuse and wiring under dash. It powered up my scan gauge tool, but also would not communicate. And even though my scan tool was powering up, I verified good voltage and grounds on OBD connector.

I read that aftermarket equipment wired up might cause issues, but I only have an amplifier wired to the battery. Haven't used the amp in years because head unit died. Either way, I inspected connection at battery and was surprised to see the positive connection of that cable was completely gone. Lug was on the battery terminal and cable end near by, but all strands of stripped end were gone???

Considering that I had no idea when that connection may have failed and any related voltage variance, I decided to disconnect battery to clean terminals and posts. While the battery was disconnected, I pulled all the ECM connectors to inspect. Found no corrosion or issues.

Put everything back together and now my scan tool is connecting it OBD system. Need to put some miles on the truck before I take it back down for smog test.

 

Hi Nasher75,
I am also have a no communication with the ECU on my 97 Tacoma. Most of the issue is caused by failing capacitors in the ECU. I found one leaking capacitor in mine and I have all the capacitors professionally replaced but still have the no communication error. My board could be damage by the leak from the capacitor.
Yours seem intermittent and you might want to google for capacitors issues on Toyota ECM since this seems to be common problem.

 

I wonder if you maybe have a spread pin in the OBD connector.

2nd gens don't tend to have that issue or really many PCM problems at all for that matter.

 

I'm in agreement with you. Took it back for smog test and once again they could not communicate with OBD. I plugged in my scan tool in the parking lot before the test and all was good.

Got it back out when they said they could not connect and all the sudden, it wouldn't even power up. If I held pressure against the wires or connector it would power up, but would not connect intermittently.

Came back home and more of the same, so I've ordered a pre-wired OBD 2 connector and will try splicing it in and try again. Starting to get annoying.

The truck is old and beat to shit, but it still runs like a tank so I refuse to give up on it. I also have 2021 Tundra TRD Pro, but I just cannot seem to let this truck go. I've had it for 18 years and it has been an absolute workhorse.