ABS and brake lights come on at the same time

Welcome to 2CarPros.

Most basic code readers won't read ABS codes. I'm not sure what you have. I will say that most times there is an issue like you described, there is a problem with one of the wheel speed sensors. There are two ways you can check. First, if you have a live data scanner that can read ABS signals, watch to see if when the light comes on if there is a variation between what each sensor is indicating the speed to be. For example, three of the sensors say 40 mph and one says 10 mph.

Other than that, you can check if the sensors are working by checking for an AC signal from them using a multi meter. The problem I see with this technique is that the light doesn't stay on all the time and what triggers it seems to be variable.

Here is a link that shows how to test a wheel speed sensor in case you want to try it:

https://www.2carpros.com/articles/abs-wheel-speed-sensor-test

Here are a few links you may find helpful when testing:

https://www.2carpros.com/articles/how-to-use-a-voltmeter

https://www.2carpros.com/articles/how-to-check-wiring

I attached an exploded view of the front sensor. There will be one on both sides.

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Let me know what you find or if you have other questions.

Take care,
Joe

Welcome back:

Those voltages sound good. Now, the rear is a different story. The input signal for rear wheel speed originates at the vehicle speed sensor (VSS). This sensor is what sends the signal to identify vehicle speed via the speedometer. So, if there is a problem with the VSS, chances are you will notice something is off with the speedometer. I attached a picture of the sensor and where it's located so you can see which one it is.

In the picture, sensor 2 is the output speed sensor and the one I'm referring to.

Are you having any issues with the speedometer?

Let me know.

Joe

Welcome back:

I need which v8 you have to confirm transmission. Also, I did see the codes. Since both front sensors have no signal and you have the C0265, I suspect there is no voltage to the electronic brake control module. Take a look at the attached pic. Check that.

Also, the sensor you have on the work bench appears to be the speed sensor. Pic 3 looks like the transmission range sensor.

If you look at pics 2 and 3, they are the entire flow chart. Here is additional information you may find helpful. However, take not of the specific one related to the problem. Most likely, there is a connection issue at the control module.
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Steps 6 of 11

Circuit Description
The ABS relay supplies battery voltage to six valve solenoids. The EBCM microprocessor applies the grounds needed to activate each solenoid. The low side of each solenoid coil has a feedback circuit to the EBCM microprocessor. When a solenoid is commanded OFF, the feedback voltage is high. When a solenoid is commanded ON, the feedback voltage is low.

Conditions for Running the DTC
The ignition is ON.
The vehicle speed is greater than 6 km/h (4 mph).

Conditions for Setting the DTC
The EBCM detects an internal malfunction.

Action Taken When the DTC Sets
C0265
If equipped, the following actions occur:
The EBCM disables the DRP/ABS.
The ABS indicator turns ON.
The brake warning indicator turns ON.

C0266
If equipped, the following actions occur:
The EBCM disables the ABS
The ABS indicator turns ON.

Conditions for Clearing the DTC
The conditions for setting the DTC are no longer present and you use the scan tool Clear DTCs function.

Diagnostic Aids

Important: Whenever the EBCM is replaced for DTC C0265 or C0266, the ABS pump motor and motor circuitry must be tested for the proper resistance. Refer to steps 7 and 8 in the diagnostic table below for testing procedures and resistance values.

C0265
Thoroughly inspect connections and circuitry that may cause an intermittent malfunction.

C0266
Replace the EBCM if DTC C0266 continues to set intermittently.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
4. This step tests if the battery positive voltage circuit can supply adequate power to the system relay.
7. A shorted ABS pump motor or shorted motor circuitry may damage the contacts within the system relay. Follow this step to prevent damage to a replacement EBCM.

The last 3 pics I added show the ECBM connectors and what the pins are for.

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Let me know if this helps and what you find.

Joe

Welcome back:

Have you confirmed that all connections are tight and not corroded?

The only thing left is the ABS module. Just for the heck of it, and don't laugh, check the brake fluid level. I have seen low fluid turn these lights on with similar conditions.

I understand you most likely already have done that, but I had to ask.

Joe

Welcome back:

You are very welcome. I'm glad it hasn't come on. Lets hope it was a one time deal. Let me know if you need anything.

Take care,
Joe