P2591: Cruise Control Front Distance Range Sensor Left
What to do
The car drives normally, but adaptive cruise control will not engage, and on most vehicles the forward collision warning and automatic emergency braking share these sensors — so assume those are unavailable too and drive as though the car will not brake for you.
Check the obvious first, because it is free. This is the left-hand sensor, and the two are mounted in different places on the car. If one sits low in the bumper it collects road spray, salt and snow much faster than the other, so a fault that always affects the same side and always in bad weather is very often just dirt. Clean that area of the grille and bumper and see whether it clears.
If the front of the car has been apart or had a knock, both sensors need recalibrating, not just the one that was touched. They work as a pair by comparing what each sees, so aligning one and not the other leaves them disagreeing — which is a fault in itself. Ask specifically whether both were done.
What this code means
A fault in the left-hand forward-looking distance sensor, on a vehicle that uses a pair of sensors rather than the single central one covered by P2583.
A two-sensor installation is not simply a spare. The pair are mounted apart from each other, and the difference between what each one sees is what gives the system its sense of where across the road an object is, rather than merely how far ahead. That lateral discrimination is what allows the system to tell a car in your lane from one in the next lane, or a stationary vehicle at the roadside from one stopped in front of you.
The consequence is that losing one sensor degrades the system in a specific and awkward way. The remaining sensor can still measure distance, but the pair's ability to place an object across the road is gone — and a system that can see something ahead without knowing which lane it is in is exactly the system that brakes when it should not, or fails to when it should. Most manufacturers therefore shut the function down entirely rather than run it on one sensor, which is the safe choice and is why adaptive cruise usually becomes unavailable outright rather than degrading gracefully.
Everything about causes applies as at P2583, and the obstruction point applies with an extra wrinkle worth knowing: the two sensors are mounted in different places, so they get dirty at different rates. One low in the bumper collects road spray, salt and snow far faster than one higher up behind a badge. A fault that is always the same side, and always in bad weather, is very often nothing more than where that sensor sits.
Alignment applies to both, and both must be calibrated after front-end work — calibrating only the sensor that was disturbed leaves the pair disagreeing with each other, which is its own fault rather than a fix.
Likely causes
Start here
- Radar sensor obstructed by dirt or snow · easy
- Radar sensor out of alignment · specialist
- Radar sensor not calibrated after front-end work · specialist
Less common
- Faulty front distance range sensor · specialist
- Corroded or loose connector · easy
- Aftermarket fitting obstructing the radar sensor · easy
Symptoms
Components involved
Information, not instruction
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Community experience
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