Discovery 4, Fixing "Camera Unavailable, Please Consult your Dealer" message

[TomHP9]

On the LR4 no fault indications from the OBD were seen. Camera is just a video feed to so no error codes. Parking sensors don’t seem to have anything either. The parking camera will stop and just show scrolling interference lines like on old TV if any part of the parking aid chain fails. The chain is everything plugged into the Parking Aid Module, (PAM), located behind the nearside boot panel, (Powerful UK has videos on removal), that is front and rear sensors in the bumpers and the module itself, but NOT the camera. THE PAM will send an error on the CAN bus (twisted pair of wires going into it) if it fails, or the sensors fail, this switches off the camera and gives the error message.

Testing the camera. From the secret menu on the display, select video test. You will get the scrolling lines. But to check there is a feed, put your finger over the camera lens and you will see a slight change. If you do, the camera is OK. If blank the camera has failed, but any cheap reversing camera will work if you are prepared to patch the video lead into it, no need to pay for the OEM version.

Testing the sensors. I found trying to listen to their high pitched sound impossible and I am not sure they even come on if the PAM has detected a fault, it might well shut them down immediately. Listening also does not tell you if the wiring is at fault or the sensor. Best way is to get a multi-meter on resistance setting. Measuring between the And pin and each of the 4 signal pins on the sensors should give a steady 10K Ohms. Measuring between the live and signal pins is a capacitive load and should show an initial reading of about 12K Ohms and rising to about 18.6K Ohms and holding. Access to these pins is either at the PAM itself by unplugging the middle connector (Front sensor) or bottom (Rear) and putting in a thin wire at the right pin and measuring. Or, the main connector block for the front sensors is underneath the offside front headlamp, (8 way block clipped to the bodywork),  which is easy to remove, or the connector is floating behind the rear nearside lamp cluster.

Any Open measurement or considerably higher resistance readings will be the sensor, or just as likely, damage to the wiring in the bumper. Good news is you have to take off the bumpers to get to anything for replacement anyway so you can check both possible issues. My recent issue led me to a failed wire on a front sensor, still hanging on by the plastic outer sheath, but the wire itself had parted, gentle tug and it came in two.

Pin outs can be found in LR wiring sheets, But at the PMA – 

Front sensor. Live is pin 2, Gnd is pin 1. Sensors: Outer LH pin 5, Inner LH pin 6, Inner RH pin 7, Outer RH pin 8, (12 pin connector)

Rear Sensor. Live is pin 11, Gnd is pin 8. Sensors: Outer LH pin 5, Inner LH pin 3, Inner RH pin2, Outer RH pin 4.

If you want to check the CAN bus at the PMA at the top connector, (larger 16 pin), you should get 60 Ohms across pins 14 and 7. 120 Ohms may be OK, anything else you have a more serious hunt on your hands and you are likely getting other errors on the OBD. To check the PMA itself, power is pin 1 and Gnd is pin 16. The rest is a black box and a swap out is the best you can do I think.