Mercedes-Benz S420 ECM-Power Relay Replacement at your home or office.

Our mobile mechanics offer services 7 days a week. Upfront and transparent pricing.

Estimate price near me

Service Location

Customer Ratings

(13)

Included for free with this service

Online Booking

Mechanic comes to you

12-month / 12k-mile warranty

Free 50 point safety inspection

Our certified mobile mechanics can come to your home or office 7 days a week between 7 AM and 9 PM.

Customer Ratings

(13)

ECM-Power Relay Replacement Service

How much does a ECM-Power Relay Replacement cost?

On average, the cost for a Mercedes-Benz S420 ECM-Power Relay Replacement is $115 with $20 for parts and $95 for labor. Prices may vary depending on your location.

CarServiceEstimateShop/Dealer Price
1995 Mercedes-Benz S420V8-4.2LService typeECM-Power Relay ReplacementEstimate$155.75Shop/Dealer Price$183.44 - $227.14
1997 Mercedes-Benz S420V8-4.2LService typeECM-Power Relay ReplacementEstimate$135.75Shop/Dealer Price$163.47 - $207.19
1996 Mercedes-Benz S420V8-4.2LService typeECM-Power Relay ReplacementEstimate$135.75Shop/Dealer Price$163.47 - $207.19
1999 Mercedes-Benz S420V8-4.2LService typeECM-Power Relay ReplacementEstimate$135.75Shop/Dealer Price$163.43 - $207.12
1994 Mercedes-Benz S420V8-4.2LService typeECM-Power Relay ReplacementEstimate$135.75Shop/Dealer Price$163.50 - $207.24
1998 Mercedes-Benz S420V8-4.2LService typeECM-Power Relay ReplacementEstimate$135.75Shop/Dealer Price$163.47 - $207.19
Show example Mercedes-Benz S420 ECM-Power Relay Replacement prices

What is the ECM-Power Relay all about?

Vehicle development has evolved over the past several decades to a point where it seems every vehicle function is controlled by a computer, right down to the engine itself. This is actually the case for the engine and its related functions as it is controlled by the engine control module, or ECM. The ECM monitors and adjusts operation and power distribution to the fuel supply and injection systems, engine timing, exhaust gas recirculation, emissions, ignition system, and several other systems. In order to dispense power to operate these other systems, the engine control module requires power itself.

The power distribution center, or fuse block, located under the hood houses most or all of the vehicle’s fuses and relays. It contains a relay for the ECM that is powered up when the ignition key is turned to the on position. This ECM power relay acts as a switch that supplies power to the ECM. When the ignition is turned off, power switches inside the ECM relay and it no longer receives battery power. If the ECM power relay stops switching as it should, you will experience vehicle problems. When the relay is stuck open, no power will be delivered to the engine control module and the vehicle won’t start. If the relay is stuck closed, constant power will be sent to the ECM even with the engine turned off and the battery will drain.

Keep in mind:

  • The battery should be disconnected any time the electrical system is being serviced.
  • There are several problems which can cause your vehicle not to start, with the ECM power relay being one of them. Have the problem diagnosed by one of our expert technicians.

How it's done:

  • The ECM-power relay is verified that it needs to be replaced. The relay is located in the engine main fuse relay control box.

  • The defective ECM-power relay is removed from the control box by pulling it straight up and out of socket.

  • The new ECM-power relay is installed into the socket and the engine scanned for codes.

  • The engine is started and the ECM-power relay is tested for proper operation.

  • The vehicle is road tested for proper operation of the ECM-power relay and is then checked for codes.

Our recommendation:

The ECM power relay should last the lifetime of your vehicle unless there is a power distribution problem or moisture that causes it to fail. If your vehicle won’t start, have one of our expert technicians diagnose the problem and replace the ECM power relay if necessary.

What common symptoms indicate you may need to replace the ECM-Power Relay?

  • Engine will not start when the key is turned.
  • Engine doesn’t turn over when ignition is on.
  • Check Engine light is on.
  • Battery drain which may leave it weak or dead.

How important is this service?

Although it is extremely unlikely the ECM relay will cause your vehicle to stall or create a safety concern, your vehicle may not start or the battery may die while the ignition is off. In either case, you will need to replace the ECM relay.

Fast and easy service at your home or office

Backed by 12-month, 12.000-mile guarantee


Meet some of our expert Mercedes-Benz mechanics

Real customer reviews from Mercedes-Benz owners like you.

Excellent Rating

(13)

Rating Summary
12
0
1
0
0
12
0
1
0
0

Kenneth

20 years of experience
801 reviews
Kenneth
20 years of experience
Mercedes-Benz S420 V8-4.2L - Oil Change - Los Angeles, California
He is the real deal... On time, did great work, very all together" good man and mechanic...... Thanks Kenneth.

Whitney

39 years of experience
783 reviews
Whitney
39 years of experience
Mercedes-Benz S420 V8-4.2L - Brake Pads Replacement (Front, Rear) - Palo Alto, California
He is great.

Richard

17 years of experience
141 reviews
Richard
17 years of experience
Mercedes-Benz S420 V8-4.2L - Fan Clutch - Sacramento, California
good guy does the job and easy to talk to very friendly!

Anthony

7 years of experience
141 reviews
Anthony
7 years of experience
Mercedes-Benz S420 V8-4.2L - Car is overheating - Sacramento, California
showed up on time did diagnostics right away he was pretty accurate.

Excellent Rating

(13)

Rating Summary
12
0
1
0
0
12
0
1
0
0
Number of Mercedes-Benz S420 services completed
143+
services done by our mechanics
TOTAL NUMBER OF EXPERT Mercedes-Benz MECHANICS
1100+
experts on our platform

Recent articles & questions

How Long Does a Hydraulic Brake Booster Last?
Being Being able to brake at a moment’s notice is important and can help to save you from an accident. A car’s braking system has so many different components and keeping them all in good shape is not an easy...
How Long Do Spark Plugs Last?
In In order to operate, your engine needs fuel and air. However, those two things alone won’t make it run. It needs a way to ignite the fuel after mixing it with air from the intake. That’s what your car’s...
How to Use Autostick
Autostick gives drivers with automatic transmissions the feel of a manual car. It allows the driver to upshift and downshift for extra control.

Car shuts off after jump-starting

Hello. It sounds like the alternator has failed (https://www.yourmechanic.com/article/symptoms-of-a-bad-or-failing-alternator) and is not charging the battery. The purpose of the alternator is to take over for the battery once the car has started. If the alternator is not working properly, then...

Car squeaks when I turn the wheel.

This is a common issue with the Audi A4 and is often times related to the control arms (https://www.yourmechanic.com/services/control-arm-assembly-replacement) in the steering. These can tend to rust and become corroded which will cause the squeaking sound you describe. There are...

My car is overheating there are no leaks all the hoses are intact and I just changed my thermostat 6 months ago. What might be cau

A diagnostic would determine the root cause of the overheating. Common causes of overheating include a faulty thermostat (yours was replaced but that is no guarantee that it is presently functioning), a plugged radiator, collapsed hoses, and a faulty water...

How can we help?

Our service team is available 7 days a week, Monday - Friday from 6 AM to 5 PM PST, Saturday - Sunday 7 AM - 4 PM PST.

1 (855) 347-2779 · hi@yourmechanic.com