How to fix ESP defective/P0120

From the interwebs..... The ESP malfunction on your Mercedes-Benz can be caused by several failed components. Instead of just guessing at what could be wrong it is better and cheaper to find a diagnostic scanner that can read the ESP fault codes. The ESP fault code will describe which of the following is the problem. It makes diagnosing such problems much easier and cheaper. Brake Light Switch – The brake light switch is located above the brake pedal, and they are known to fail frequently. They are very inexpensive parts and can be replaced in as little as 15 minutes. If you need to know how to replace the brake light switch yourself check out this article on How to replace the Brake Light Switch on a Mercedes-Benz. ABS Wheel Sensor – The ABS wheel speed sensors can fail and cause the ESP light to turn on. Replacing the ABS sensor is easy, you can learn how to replace ABS sensor here. Note that once you will replace the ABS sensor and will still have the ESP warning light on. You will need to follow the procedures below to reset the light. Low Battery Voltage – If you have an old Mercedes-Benz battery which is not supplying the needed voltage you can cause ESP malfunctions and a variety of other problems such as ABS and ETS warnings. This is tricky because the battery may start the car just fine, but it doesn’t maintain the requried voltage while the car is running. Check the age of the battery (there should be a sticker on the battery wiht mo/year) and replace if it is over 6 or 7 years old. Once you replace the battery reset the ESP light using the instructions below. Replacing the battery is not that difficult and you can replace it yourself in less than an hour. Read this article if you need to learn How to replace the Mercedes-Benz Hint: In that article, we make suggestions on were you can buy Mercedes-Benz at a reasonable price. ABS Module – The ABS module does the hard work when electronic stability program (ESP) engages. It brakes the individual wheel to help the car stay on the road. If the ABS module is not working properly, you need to replace it or repair it. A new module can be very expensive, but you can also find ABS module repair service on eBay that will fix your existing module. Mercedes-Benz ABS / ESP Pump Repair Service Steering Angle Sensor – is right behind the steering wheel in the steering column. It’s the main purpose is to calculate the angle of the steering wheel so that the car knows if you are taking a turn or if you are going straight. The input from the steering angle sensor is used by the ESP control module. The steering angle sensor doesn’t usually fail, but they may need calibration. You can use a scanner such as the iCarsoft MB II to read the steering angle sensor values and correct the problem. Further ESP Light Diagnosis Before you can turn off the ESP light, you first need to find the cause of the ESP light and fix the problem. As you saw above there can be several issues that can cause the ESP light. The easiest and quickest way to diagnose what is causing ESP light to stay on is to use a professional scanner. You can borrow such a scanner from a friend or consider buying your own. There are a couple professional scanners that are reasonably priced which we have listed above. If the ESP button did not shut off the ESP light, then the next thing to do is to check the fuses. Look under the hood and on the side of the dashboard and you will find two fuse boxes. In there you should have a fuse chart. You can remove the fuses to check if any of them are blown or you could use a fuse tester to quickly test all the fuses without removing them. Removing the negative battery terminal will not erase the ESP light. Disconnecting the battery works for resetting the check engine light but will not function for clearing hard codes such as ESP, ETS, 4ABS Resting Mercedes ESP Light If you need to further diagnose the ESP warning light, you will need an advanced OBD-II scanner that can read ESP codes. You can take the car to the Mercedes-Benz dealer who will scan the vehicle with the Mercedes-Benz Star Diagnostic or an independent auto repair mechanic who typically use theAutel DS708. Or instead of paying someone else you can do the same thing yourself using a scanner such Launch Creader or iCarsoft MB II which are reasonably priced. These scanners cost about as much as it costs to get your Mercedes-Benz diagnosed one time. RESET ESP LIGHT YOURSELF Instead of paying someone else to read the ESP fault codes and reset the light, you can do the same thing yourself using a scanner such Launch Creader or iCarsoft MB II. These scanners are reasonably priced and cost about as much as it costs to get your Mercedes-Benz diagnosed one time. In the following video, we will show you how to reset the ESP light using Launch Creader. The steps are very similar on iCarsoft MB II. Both scanners have the same interface but iCarsoft MB II is a scanner for Mercedes-Benz cars only and can scan more systems. The Launch Creader can scan other makes and models such as BMW, Audi, Lexus, Toyota, Honda and can read and erase fault codes for transmission, ABS, engine, airbag, ETS, SRS. Launch Creader VII Diagnostic Scanner – All Makes iCarsoft MB II Mercedes Specific Scanner Don’t waste time replacing parts without first reading the fault codes using one of the scanners mentioned above. Within minutes you will know the cause of ESP light staying on and erase the ESP fault codes. The ESP light could have been triggered by something as simple as low battery voltage. In that case, you just need to read the ESP codes and erase them Mercedes ESP Light – Frequently Asked Questions What causes ESP on Mercedes-Benz C, E, S ML Class? Mercedes E-Class W210, W211 ESP light If you have the ESP light on your E-Class, one thing you may want to check is the brake light switch. This is a common problem with the E-Class. In some cases, the gear shifter can cause the ESP light to illuminate if liquid gets spilled on the shifter. Mercedes C-Class W203 W204 ESP light -ESP light on a C-Class is typically caused by a defective brake light switch or low battery voltage. Mercedes Benz ML-Class W163 W164 W166 – A common problem that causes the ESP light to come on in Mercedes-Benz ML models is the ABS pump. Brake light switch is also a common problem in this model too. Can I reset Mercedes-Benz ESP light using an OBD-II scanner? A $20 or even a $50 OBD-II scanner that read the check engine light is not able to read other control units. These scanners are typically loaned for free from Advance Auto Parts or AutoZone, but they will not reset your ESP light or read the fault codes. You need a professional scanner such as iCarsoft MB II or Launch Creader VII Can I reset the ESP light by disconnecting the battery? No. Disconnecting the negative or positive terminals of the battery does not erase the ESP light. Is it safe to drive the car if the ESP light is on? It is as safe as driving a car that doesn’t have ESP. Many cars on the road including entry level new models such as Mazda, Honda, Hyundai do not have ESP. Is it safe to drive them? Only, you can answer that. You will not have the added safety feature provided by ESP. If you lost traction while going around a curve, there would be no ESP to help you out. The only thing that may limit you driving your Mercedes-Benz if the ESP light is on could be if the car goes into limp mode. This can happen depending on what is causing ESP problem. In which case the transmission will not change gears, and you can’t accelerate past 20mph. If the car doesn’t go into limp mode, then drive carefully and don’t ignore the problem. Get the car repaired as soon as you can. How can I turn off Mercedes ESP completely? Some of you may be wondering how you can completely turn off ESP so that you can be in charge of the car and be able to spin the wheel. Well just turning ESP off via the switch doesn’t completely turn off ESP. In extreme situations ESP will still engage. You can disable ESP either via the secret menu using the multifunction buttons on the steering wheel, by using a scanner such as Mercedes-Benz DAS Star Diagnostic to disable ESP Control Unit or by removing the ABS / ESP fuse. You shouldn’t disable ESP unless you understand the risks of not having ESP / ABS.