Gauges Don't Work ABS and AirBag Light On

Googled and found bunch of different answers but none help so far.

Truck is a friends 08 5.7L Tundra.

Gauges don't work. Only fuel and battery gauge works. ABS and Airbag light is on.
OBDII port doesn't communicate with scan tool.

We have tried the zero point calibration no luck.

Also heard it was the steering angle sensor or wheel speed sensor. But is there any way to confirm which one before we start throwing parts at it.

 

The entire CAN bus is down then. No data moving on the communication line between the ECUs. This is what drives all the gauges, let’s the ABS computer talk to the cluster ect. Pulls data in and out of the OBD port. It’s literally the main communication between all the ECUs

More details on how this started?

 

Just died one day. Drove it around for couple months and came back on while driving in rain.

Then couple weeks later went down and stayed down for the past couple months. Since it came back on while it was raining we were thinking maybe the wheel speed sensor but no idea how to figure out which one.

 

If you really think it is a wheel speed sensor, unplug them and see if the communication comes back. I would assume it is possible that a sensor could short out and cause the CAN system to go down. Additionally you might just have a bad spot in the wiring. There is a wheel speed sensor on each wheel and on the rear the wiring comes down the axle and then joins up at a connector under the bed. Look around in here for wires with no insulation touching each other or the frame rail.

You can go one by one at each wheel and unplug the connector to each wheel speed sensor. If unplugging one of them makes the gauges etc. work again this is most likely your problem.

The wheel speed sensors send a signal to the ABS ecu which then broadcast that signal out the communication line. Something somewhere is shorting out your communication line and not letting data through. If you really wanted for a quick test, you could complexly unplug the ABS ECU, removing it from the circuit entirely to see if the communication line starts working again. Doing this would also remove all the wheels speed sensors ect from the equation. If the communication line starts working again with the ABS ECU disconnected you know your problem is somewhere in this circuit you unplugged.

Do not drive it will the ABS Ecu unplugged, you can start it or just turn the key on to check if OBD port works or RPM gauges ect. The ABS Ecu is under the hood on the driver side fender well closer to the firewall. It almost looks like a black pump with steel brake lines coming in and out of it. If you look closely there will be a large black rectangular electrical connecter coming into it. If you simply unplug it here it will remove the entire ABS ECU, wheel speed sensors, ect from the equation.

Could be worth doing for a fast check to help narrow down where your problem is. I assume it will create more trouble codes but they can be cleared out once its plugged back in and the communication line working again.

 

Will try unplug one by one. I don't know for sure its that but just going off google stuff I found.

I assumed unplugging them would cause the same issue but I guess you are right a short is different from a open.

 

When the truck is parked they are reading 0 anyway when working properly. Unplugging them should not effect the communication line between say the engine ECU and cluster. As mentioned the problem could be if a sensor or sensor wiring is shorted out jamming up the communication signal line.

The ABS ecu send the signal on the Comm line, not the Wheel Speed sensors. I would defiantly try unplugging them one by one. You could also just unplug the Steering Angle sensor, its is wired directly to the communication line.

 

Well finally got around to looking at it.

Unplugged the wheel speed sensors one by one and nothing. Also un-plugged the ABS module and nothing.

Didn't around to the steering angle sensor guess thats next on the list.

 

Just for future reference in case someone has the same issue.

It ended up being the steering angle sensor that was blocking communication to the ECU. Found a used one on ebay swapped it and everything is back to normal.

Do not mistaken this for the clock spring. The steering angle sensor and clock spring are physically together when you remove it from behind the steering wheel but it can be ordered separately.