Signs & Symptoms Of Bad FICM Relay (Explained)

Ficm relays play a vital role in providing the critical transfer of amperage from the charging system to the FICM. It is located under the hood on the driver’s side fender in the fuse panel next to the firewall.

However, you won’t get the proper output from a faulty ficm relay. So, you should check out the symptoms of bad ficm relay to figure out the electronics’ problems.

Signs of a Faulty Ficm Relay

The most common and obvious sign of bad ficm relay is the hard starting of the vehicle, overheated relay, a clicking noise coming from the starter, and codes.

What Are The Symptoms Of Bad Ficm Relay?

There are other significant symptoms by which you can easily identify when your ficm relay needs proper inspection and repairing or replacement. 

So, let’s learn more about those symptoms and how to detect a bad ficm relay-

1. Sending codes

The relay’s primary job is to give power to the control modules needed for the engine to run. But if you get codes like U-0105 Lost Communication with FICM, 611 code on a non-voltage modified FICM, this indicates faulty ficm or ficm relay. 

If your voltage is solid, it may be that the issue is with the logic side of the unit.

2. Overheated 

The FICM relay can get hot and then it can lose power to the FICM. This also indicates a bad relay. 

3. FICM Failure

The power supply generates the voltage that the logic board uses to control the fuel injectors. But there are many ways for a FICM to fail but the most common failure is the ficm power supply itself.

The FICM power supply is designed to produce 48 volts. A failing ficm power can be identified when the voltage drops below this requirement. 

A low voltage ficm can cause less than perfect combustion within the engine. This can lead to poor performance and poor fuel economy.

You can encounter hard starts and slow running when the engine is cold. 

4. Hard Start

One of the common symptoms that usually indicates a bad Ficm is a hard start.

If the vehicle cranks long than normal and starts and runs rough, firstly we need to check the Ficm. 

How To Detect A Bad Ficm Relay?

If a component isn’t working because electricity isn’t getting to it, there is a possibility the relay may be faulty. But determining whether or not a relay is defective requires a little basic investigation.

And thankfully, testing a ficm relay is a task that even amateur mechanics can handle.  

Check the wire harness

A faulty wire harness can cause this problem. You need to check for chafing on the wire harness –

  • Underside of the ficm connectors
  • Edge of the valve cover
  • Around intake manifold bolts
  • Between oil filter housing and turbo

Then clean the battery connections properly to avoid problems.

FICM test

To see if you are getting a good voltage, you need to measure on the pin closest to the driver side. 

Then, take a multimeter. Set it to volts DC and hook your ground to the ground on the battery. You are going to use your positive lead to check for voltage at that pin. Now, touch the probe to the pin not the case of the ficm as that will cause a short. Then turn the key on. 

Be aware – Don’t start the vehicle 

How To React When You Found Out A Bad Ficm Relay?

There are some steps you can do except replacing the relay to get rid of the faulty one. 

The symptoms may point to a troubled logic board. Logic board failures and wiring harness chaff that cause a short or a bad alternator are the common causes. So, you can change the alternator which is a cheap solution. Again, if it’s just a bare spot on a wiring harness, liquid electrical tape with a vinyl tape wrap is cheaper yet.

The voltage drops of the ficm relay you have encountered are indeed caused by the load of the glow plugs and the alternator’s inability to keep up with that load.

The 185 amp OEM series comes with 100 amps at hot idle, 120 amps at cold idle. This might not be enough to offset the glow plug draw, but it sure gets closer.

If you don’t have budget issues, you can move to the 190HD series or 270XP, which does 140 amps at cold idle and 200 amps at cold idle respectively.

Is Replacing Ficm Relay Is Expensive?

When you have heard the symptoms of a bad ficm relay, you may want to replace it immediately. 

Since bad relays can kill FICM, it is a good idea to just replace it every 100k for good measure.

The average relay replacement cost is between $15 and $80, depending on the model and labor costs. A relay costs $30 to $50 and labor costs $10 to $50.

The ficm relay itself is often very cheap, and you can expect it to cost under $30, depending on if you want to buy an original one or aftermarket.

And though the replacement of the relay is also often very straightforward, you can expect a replacement cost of $15 to $100 if you want a mechanic to do it instead.

How Often Should You Replace The Relay? 

The replacement of the ficm relay depends on the trouble codes. If you have a Ficm performance code, you need to check the voltage first. 

If you can detect a high side fault for the eight injectors, your FICM needs to be replaced. 

You can use a scan tool to detect the FICM voltage. The voltage should be between 46 to 48-volt range. And as I said earlier, you can also test the FICM by removing the small cover and using a regular multimeter.

The Verdict

When it comes to a vehicle’s electronics, there’s a decent chance the problem is related to a relay. Keep in mind the symptoms and work accordingly.

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