ABS light on. Can't get codes

I have a 2004 Mustang GT with auto. The ABS light is on. I have a Launch code reader. I can't get codes for the ABS. it says not equipped or on connection. Were do I start looking? I checked the fuses they are good. The brakes work fine. The light was on when I bought the car. The power steering pump was bad, didn't put out enough pressure. I replaced the front calipers. The outside s were pitted the inside were fine. I also replaced a pads. Brake hoses look good. The wheel sensors look good as to the tone rings. Don't know if the sensor work correctly or not. I want to check all the electrical connections grounds for the PCM and ECU . Not sure were they are located. Just need to get the reader to work. It reads OBD2 ABS and SRS.
 
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Try another code reader. The main issue with those bidirectional Chinese scan tools is they tend to have communication issues. It’s not unheard for them to simply not communicate, compared to something like an Autel.

I have an Xtools D7 and it will see the ABS module and any DTCs stored on my ‘00.

If you have a laptop you can also install ForScan and just grab a obd2 to usb interface. Will lets you see modules and run basic service procedures like ABS test functions. In theory a good scan tool should also allow you to do this as well.

The ABS on these cars is pretty simple. 4 wheels speed sensors and hubs, and a central Brain. Most ABS codes will either be a sensor issue, or an internal issue with the ABS module itself. You can check the sensors (without codes) by unplugging each sensor and measuring resistance. A bad one will be open.


Edit: you didn’t say what model Launch scan tool you have. Some of the lower trims won’t read modules and just do OBD2 data.
 
Try another code reader. The main issue with those bidirectional Chinese scan tools is they tend to have communication issues. It’s not unheard for them to simply not communicate, compared to something like an Autel.

I have an Xtools D7 and it will see the ABS module and any DTCs stored on my ‘00.

If you have a laptop you can also install ForScan and just grab a obd2 to usb interface. Will lets you see modules and run basic service procedures like ABS test functions. In theory a good scan tool should also allow you to do this as well.

The ABS on these cars is pretty simple. 4 wheels speed sensors and hubs, and a central Brain. Most ABS codes will either be a sensor issue, or an internal issue with the ABS module itself. You can check the sensors (without codes) by unplugging each sensor and measuring resistance. A bad one will be open.


Edit: you didn’t say what model Launch scan tool you have. Some of the lower trims won’t read modules and just do OBD2 data.
I will try to get codes off My 2011 Chevy Silverado. The code reader is brand new. there are a lot of videos about this reader all good. so if it works on my other vehicle then it should be good to go. Thanks
 
The reader works perfectly on t=my 2011 Chevy Silverado So the reader is not the problem. What would keep the reader from seeing that codes on the ABS system? It sees the engine codes. So the OBD plug is working ok. I guess it could be one of the pins? Could it be the ECU not connecting to the ABS system?
 
The reader works perfectly on t=my 2011 Chevy Silverado So the reader is not the problem.

This is not proof that it will pull codes from your GT. If you have the opportunity, try a different reader just so you're not chasing ghosts.

Could it be the ECU not connecting to the ABS system?
This is a possibility. A broken connection would certainly trip the light.

I've seen instances where folks reseated the main ECU connector and cleared up stuff like this too.
 
I have a 2004 Mustang GT 4.6 auto. Bought it used. When I connect it to ECU 16 pin port. It shows it isn’t connected to ABS. Also most of the protocols fail. The car runs good. The reader doesn’t see the VIN number. Could it be the car has a ECU out of another car? If so can I get it flashed to get ABS back working and so I can use my reader to diagnose the car in the future? I only get one code now for the intake air temp? Thanks
 
Is this the style abs block you have?-
IMG_8142.webp

If so-maybe start with that connector, here’s a quick pin out I found-
IMG_8144.webp
IMG_8143.webp


I’d check for power-continuity etc,maybe there is a broken wire in the harness?
 
I have a 2004 Mustang GT 4.6 auto. Bought it used. When I connect it to ECU 16 pin port. It shows it isn’t connected to ABS. Also most of the protocols fail. The car runs good. The reader doesn’t see the VIN number. Could it be the car has a ECU out of another car? If so can I get it flashed to get ABS back working and so I can use my reader to diagnose the car in the future? I only get one code now for the intake air temp? Thanks

What code did you get, exactly?