Technical: Why Recalibrations Fail

Why Your Recalibration of a Vehicle’s Electronics Failed

Knowing what may have blinded the sensors can save time in knowing why a recalibration may have failed.

Scanning vehicle electronics is a totally different process than recalibrating a vehicle’s electronic features.

A scan tool can tell you if the computer and modules can communicate, whereas a recalibration can verify that the electronics can see where and what they’re supposed to. This is critical for all new crash-avoidance features in vehicles today, such as forward crash warning or advanced driver assistance systems (ADAS). Depending on if you’re doing your own recalibrations or subletting them, you’ll find that sometimes recalibrations fail. Knowing what was done and what has blinded the sensors becomes important to not waste time and energy when trying to figure out the reason for the failure. So let’s look into why recalibrations fail and what can be done.

OEMs Say

First, let’s look into what the vehicle manufacturers are trying to say. Nissan put out a statement saying not to use aftermarket bumpers in repairs of their vehicles because the sensors were tested on Nissan’s exact specifications of material and thickness. Before everyone gets riled up, I’m not here to debate OE versus aftermarket.

Nissan is saying they have a concern when it involves the sensitivity of sensors that are involved in the ADAS. The size or thickness or even the material of the part, if not made to manufacturer specifications, could create a problem. From the beginning, sensors are calibrated and tested by manufacturers to work through a specific parameter or tolerance. Sensors are also aimed and calibrated to the vehicle centerline and/or ride height.

In the case of aftermarket parts, what happens if the part is thicker than tolerances allow? This could give a faulty reading. What if the part has sensor holes that are slightly different or not straight in the way the sensor mounts? Again, these specifications are designed for the optimum performance of the vehicle’s safety features. If you make a business decision to use these parts, then you’ll have to verify that they work properly. This is where recalibrations come in. No matter if you use OE, aftermarket or salvage, any time you R&I or replace a part that is part of the safety features, it should be recalibrated.

Mil thickness of paint or plastic repair on a bumper may interfere with the sensors.

Let’s look at a Ford Mustang. A quarter panel has been replaced. In the process of R&I’ing the bumper, the estimator found that an azimuth test should be performed to verify the sensors in the bumper work correctly. A post-scan shows no codes and that all electronic modules are communicating correctly. The azimuth test requires that targets be placed in specific locations to test the sensitivity of the bumper’s object detection sensors, which are vital to many safety features. Let’s say the test specifications for sensitivity fails to meet the parameters. So what should we look at first? Since a recalibration is a pass/fail test, there’s no issue pinpointed or code. You may be able to tell which sensor is the problem depending on which diagnostic tool you use, as it may allow the testing of each sensor individually. If you don’t have that capability, you would need to do a process of elimination:

  1. Check all connections. Scan tools may not be able to test some aspects unless the vehicle is in motion. Therefore, a scan test may not send out a DTC until 35 mph is reached.
  2. Was anything replaced?
  3. What was added?
  4. Could anything be interfering with the test?

In this case, the connections are good. The bumper cover was R&I’ed, so we know we’re good there. So what was added? In this case, the bumper was refinished. The repair added mil thickness to the paint on the sensor and blocked sensitivity. This is fairly common in the repair industry. Many sensors can be painted but not refinished. Also, sanding for refinish can damage sensors too.

Plastic repair can also interfere with sensors. In many vehicles, Doppler radars are mounted on quarter panels. A plastic repair on or near the point where the radar operates can severely limit or stop the blind spot detection system from operating correctly, or operating at all. Most shops do not do a test to check for proper operation of these sensors. Most shops think that if there is no light, it must be right. That can be a major liability and dangerous thinking for the family driving the vehicle. This is just an example of one situation.


R&I of a windshield or replacement of a windshield is a fairly common procedure done on vehicles. In this example, we’ll use a Subaru.

In the process of removing the windshield, the camera mounted at the top of the windshield will be removed from the mount. This camera was aimed at the factory for optimum performance of the forward crash warning and lane-departure system. It’s a vital component to either reduce the forces in a crash or prevent one altogether. It’s also part of the pedestrian protection system. The aiming and sight of the stereo camera system is critical to operation of all these ADAS features. Moving the camera requires that it be recalibrated, even if it was never disconnected.

Subaru states in their service procedures and even in the owner’s manual that the windshield used must be a Subaru genuine part. Not using a Subaru genuine part may not allow the crash avoidance and lane-departure functions to work as designed. Subaru is not the only manufacturer to have stated this; Honda and many others have stated this too. There is a very viable concern as to why they say this; it’s not just to sell glass. In the case of the ADAS cameras, the windshield is a front lens to the camera. Tolerances of non-genuine parts may interfere with the camera’s ability to focus through the glass – kind of like getting the prescription wrong on your glasses or contacts. It blurs the vision.

When removed, windshield-mounted cameras like this one will need to be recalibrated.

There is also another point to this. Subaru and other manufacturer dealerships in many cases will not perform the camera recalibration on vehicles that don’t use genuine glass. I’ve had some dealers do the recalibrations, but if the recalibration fails, the first thing they’ll say is the windshield is wrong. They too are using the process of elimination. In their case, the most obvious choice is the glass as the problem. An assumption is made that it worked fine before the glass was replaced. Rather than take the time to find an electrical problem or replace an expensive camera, the dealership will not proceed until the windshield is replaced using genuine glass, which in reality is common sense. Again, a recalibration may not be able to pinpoint why a vehicle can’t see and why there is no DTC light on the dash. So what changed? In many cases, the glass is the issue for the failed recalibration. This is not to say that aftermarket glass can’t be recalibrated; this has been done successfully the majority of the time. There can be many issues affecting the camera.

In one situation, a windshield was being replaced again and the technician was going to install Subaru glass. During the installation, a spider web was found in the camera. It was determined that the spider web was the culprit, not the glass.

Also, brackets that hold cameras to the glass can be mounted wrong. For example, if a bracket is so tight on the aftermarket glass that it breaks the bracket during attachment, this slight break could cause the recalibration to fail.

Recalibration Issues

The recalibration of the camera system is not infallible. There are other issues that can affect the process besides the glass.

  1. Static tests. A static test is done with black-and-white checker board targets mounted on a target board. During the recalibration, sunlight patterns in windows can affect the test. An employee wearing a black or white shirt may create a problem. Even colored background walls can cause failures. The recalibration on these cameras is a relatively sensitive process.

Here are some highlights from one automaker:

  • Make sure there are no black-and-white patterned objects in front of the vehicle.
  • Be sure to perform the measurement on a level surface that’s free of obstacles and extends 1.5 m (4.92 ft.) or more in front of the vehicle.
  • Make sure that there is no wind when performing the measurement.
  • Check that there are no reflective materials in the surroundings or on the ground within a 3 m (9.84 ft.) x 3 m (9.84 ft.) area in front of the vehicle.
  • Perform the inspection in a bright area.
    • Prepare for camera axis learning.
      • Move the vehicle to a level surface.
      • Make sure the engine oil in the vehicle is at the specified level.
      • Make sure the engine coolant in the vehicle is at the specified level.
      • Make sure the fuel tank is full.
      • Make sure the spare tire is in the vehicle.
      • Make sure the standard tools are in the vehicle.
      • Make sure nobody is in the vehicle.
      • Make sure no extra loads are in the vehicle.
      • Adjust the tire pressures to the specified pressure.
      • Clean the windshield.
    • Perform front wheel alignment adjustment.
Black-and-white checkerboard targets used during a static test.

2.Dynamic tests. These are done while driving. If it’s raining or snowing, the test will fail. This involves hooking up the diagnostic tool to the vehicle and driving at speeds over 35 mph on well-marked roadways. If there is any weather preventing the markings from being seen, the dynamic test will fail.

Here are highlights from one manufacturer:

The ideal calibration condition is driving on a two-lane divided highway with markings on both sides of the lane.

To calibrate the front camera, operate the vehicle in the following conditions until the calibration is complete:

  • Clean the windshield.
  • Avoid lane changes.
  • Maintain vehicle speeds between 56–90 kph (35–56 mph).
  • Ensure the road contains visible references (well-defined lane markings, curbs, etc.).

One or more of the following conditions may increase the length of time required to complete the self-calibration procedure:

  • Heavy traffic.
  • Stop-and-go traffic.
  • Mountain roads.
  • Curves in the roadway.
  • Poor contrast lane markings.
  • Botts’ Dots type lane markings.
  • Operating the vehicle at speeds greater than 90 kph (56 mph).
  • Driving through snow or fog, or driving directly into the sun.
  • Camera not properly installed; verify that it’s snapped into tabs and is secure.

Conditions that will prevent completion of the self-calibration procedure:

  • Dirty windshield glass or obstruction on windshield.
  • Operating the vehicle at speeds less than 56 kph (35 mph).
  • No visible lane markings.
  • Severe weather where lane markings cannot be seen.
  • Camera not properly installed. Verify that it’s snapped into tabs and is secure.


As more and more of these procedures are being required, we need to be sure to look up and follow them. When problems arise, the process of elimination will be needed to correct them. Education is the best way to prepare for any problems. Understand the process and why these processes are used.

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