My back lights stay on when I start the car and turn on the lights. When the car is off the back up lights do not come on. Any ideas or do I need to take it to ford. They are factory lights
Rear lights
- Thread starter sabrooks
- Start date
bradleyem
Member
On these cars, the backup lights are controlled through the CAN bus, so this could be difficult to troubleshoot.
The PCM (Powertrain Control Module) gets a signal from either the reversing lamp switch (manual transmission) or the DTR sensor - Digital Transmission Range Sensor (auto transmission). This is then converted into a data signal within the PCM, and sent via the High Speed CAN Bus to the instrument cluster. Then it is converted to a Medium Speed CAN signal and sent to the low current board of the Smart Junction Box in the passenger kick panel. The Low Current Board then sends power to the reversing lamps.
Typically it is easy to check is the reversing lamp switch on the transmission if you have a manual transmission. It is just an open/closed switch on the transmission that would be closed when the transmission is in reverse. This can be checked by using an ohmmeter, short circuit tester, etc. You would want to find the switch on the transmission with 2 wires, one of them is Violet with a White stripe, and the other is Grey with a Red stripe. Just put a tester on it (disconnect the switch from the harness first) and make sure that it opens/closes when you put the transmission in and out of reverse.
Since most of the rest of the circuit is Data, if the switch is good, the most likely problem would be with the Smart Junction Box. Since the reverse lights only come on when the parking lights are on (Correct?) there may be a short in the SJB Low Current Board. One likely cause of this is if you have (or have had) the dreaded passenger side water leak. If the SJB has gotten wet, and corrosion has formed on the circuit board, then this could cause symptoms like you describe, as well as lots of other wierd electrical gremlins.
The PCM (Powertrain Control Module) gets a signal from either the reversing lamp switch (manual transmission) or the DTR sensor - Digital Transmission Range Sensor (auto transmission). This is then converted into a data signal within the PCM, and sent via the High Speed CAN Bus to the instrument cluster. Then it is converted to a Medium Speed CAN signal and sent to the low current board of the Smart Junction Box in the passenger kick panel. The Low Current Board then sends power to the reversing lamps.
Typically it is easy to check is the reversing lamp switch on the transmission if you have a manual transmission. It is just an open/closed switch on the transmission that would be closed when the transmission is in reverse. This can be checked by using an ohmmeter, short circuit tester, etc. You would want to find the switch on the transmission with 2 wires, one of them is Violet with a White stripe, and the other is Grey with a Red stripe. Just put a tester on it (disconnect the switch from the harness first) and make sure that it opens/closes when you put the transmission in and out of reverse.
Since most of the rest of the circuit is Data, if the switch is good, the most likely problem would be with the Smart Junction Box. Since the reverse lights only come on when the parking lights are on (Correct?) there may be a short in the SJB Low Current Board. One likely cause of this is if you have (or have had) the dreaded passenger side water leak. If the SJB has gotten wet, and corrosion has formed on the circuit board, then this could cause symptoms like you describe, as well as lots of other wierd electrical gremlins.
Thanks I am taking it in on Saturday and yes it is under warranty. Just wanted to know if there was a quick fix
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