No Crank / No start / No OBD communication / No CAN bus voltage

Daughter bought a 2006 4.7 2WD tundra with 90k miles on it. Since she was getting ready to leave for Virginia for a year I thought I'd be helpful and change the timing belt for her. I've done this job on many vehicles before.

Got everything put together and have a no crank / no start situation. If I jump the terminals in the starter relay box the starter spins the engine no problem. Starter relay is not getting voltage when I turn the key to start. The 5A fuse in the fuse panel is getting voltage when I turn the key so dont think its the ignition switch.

checked all fuses. swapped battery with known good battery

OBD scanner will not connect with the computer. Tried several scanners, none work

Check the CAN bus voltage at the OBD DLC port and have no CAN bus voltage on high or low side. I do have 12V on the battery pin in the DLC port

Any ideas? I suspect I pinched and possibly shorted the wires to the crankshaft position sensor when installing the water pump. Replaced this section of wiring with new shielded cable but still have the same issue.

Thanks for any insight

 

I was just about to say, I believe this could totally be caused by crankshaft position sensor being unplugged, if I understand the circuit and operation correctly.

 

Even the 7.5A STA fuse next to the starter relay ?

The OBD/DLC is protected by a 7.5A fuse also, driver kick panel,

Noticed anything else not coming on in case you blew a major fuse ?

 

OBD fuse is good. Everything else seems to be working. Another clue might be that the CEL does not illuminate at any time, even during the light test when you first key on

 

I still haven't ruled out he Crank sensor but I think that would be a "crank no start" failure instead of a "no crank" failure


"

 

Ah, yes. Misreading on my part. I agree with Bubba's line of thinking here.

 

The CPS came up it another thread the other day and comments concerning will it prevent from running. To satisfy my curiosity, I unplugged the CPS and it indeed ran. Of course I was not up to temps, meaning I was not in closed loop and the ECM is not needing that sensor nor other sensors while in open loop.

All that to say, it’s normal IMHO. My CEL light was not on even with IgnOn/Eng/Off after that test. Having unhooked batt, I performed readiness monitors and a few drive cycles before CEL started acting normal.

 

I've traced and tested enough wires to know that it is the ECU that is keeping it from starting. When I turn the key to start position there is 12V going into the ECU but the wire that leads from the ecu to the PNSW, TVIP and eventually the starter relay is not energized.


So something is telling the ECU that the engine is not safe to start. Does anyone know of a source for the logic used in this circuit? In other words, what must be true for the ECU to tell the truck to start?

Thank You

 

I'd recommend you hit this thread, and check the comma-separated list of documents in the (5th?) paragraph to grab the appropriate service manual for your truck: https://www.tundras.com/threads/so-you-wanna-buy-just-bought-a-1st-gen-tundra-eh.115928/

 

You were in the right area, I just didn't check far enough. The truck will run with the cam sensor open but not with it shorted to ground. Somewhere the camshaft sensor harness is shorted to ground which is killing the 5V reference voltage. unplugging the sensor let it try to start. Now I just have to find the short

 

Read that earlier this AM while in dr office and silently said BS....however, I will take that BS back with new info...."but not with it shorted to ground"

Which of the 3 conductors was it color wise ?
2 go straight back to ECU and other goes to a junction

 

The green and black one

 

Was reading a TIS Technical Training article about our Engine Control System, in particular ECM and remembered this part of your thread title....No OBD communication / No CAN bus voltage and thought I would share after the fact.
The green/black was VC signal to CAM sensor.