How To Check Your Ford Mustang CCRM

How To Check Your Ford Mustang CCRM


Electrical problems with your Ford Mustang are never a fun time, but they don’t have to be overly difficult either. Issues with your Ford Mustang Constant Control Relay Module (CCRM) can lead to problems with your cooling fans, and can even cause your Mustang to not start. Today we’ll be showing you How To Check Your Ford Mustang CCRM, part number F6SZ-12B577-AA.

This module consists of four separate relays which control several components, the Ford Mustang PCM, as well as the fuel pump and cooling fans. When issues arise from this pack of relays your Ford Mustang may buzz or emit a strange noise. Although we’ll be showing you how to check your Ford Mustang CCRM with a 1996 Ford Mustang Cobra, this guide applies to all 1994-1998 Ford Mustangs.


Before you start our DIT CCRM guide, it’s a good idea to understand what the CCRM does and how it controls your fans. Fan speed and operation is controlled by your CCRM which uses a two speed relay in conjunction with the air conditioning relay.

When your Ford Mustang Engine Coolant Temperature (ECT) sensor reaches 210º F, this will activate the low speed setting of your cooling fans. If the temperature rises above 220º F or your air conditioning is switched on the fans run on high speed.


Turn your Mustang on and let it idle until it reaches operating temperature. Your low speed cooling fan should turn on at this point. If your fan does not turn on, make sure to check the fuses in your fuse junction panel to make sure that this isn’t your problem.


If your fuses check out okay, make sure to check your cooling fan connector. Depending on your model of Ford Mustang, your cooling fan connector is either a two pin connector, or if you own a 4.6 L like our Cobra it will be a three wire connector.


Have a friend sit in your Mustang and turn the vehicle to the “ON” position but do not start the engine. Your three pin Mustang connector should be a red wire with orange stripe for the low speed fan signal. The orange wire with blue stripe is the high speed fan signal, and you’ll be testing that last.

Take your multimeter and we’ll be testing for fan voltage with your engine hopefully still at operating temperature. If you are not sure how to use a multimeter or voltmeter, check our guide here. Take the black ground lead of your multimeter and set it against the negative battery terminal.

Although the black wire on the three pin cooling fan connector is a sensor ground, never use engine harness grounds as primary leads when testing. With the vehicle warmed up and ECT triggering the PCM, there should be voltage at this red / orange wire. Now have your friend depress the air conditioning button, and check the orange / blue wire for voltage.

Make sure your three pin connector is properly grounding your Ford Mustang cooling fans by switching your multimeter to the ohms scale and grounding the lead while touching the black wire. If you are trying to learn how to check your Ford Mustang CCRM because your 3.8 liter cooling fans will not turn on, you will have a two wire connector.


Black is ground and the red wire will be the power wire. You can have your friend simply turn on the air conditioning to check the voltage wire in question.

If you do not have voltage at these wires, you will have to track back to your Ford Mustang CCRM, which is located in your right fenderwell. If you are trying to learn how to check your Ford Mustang CCRM because of other issues, such as your fuel pump, use the diagram below to measure and test each wire in question.


If your engine sensors are not receiving power, you will definitely want to check your CCRM. Before opening your fenderwell however, always check your fuse panel, as well as your ignition switch. With the key turned to the “ON” position, you will now be testing for power at your CCRM by checknig PIN 12 and 24 for switched power.

The next pin you will be checking is pin 8 and 10 for constant power from the battery. If you do not have grounds at your sensors, check pin 15 for low reference ground signal.

If your Ford Mustang fuel pump is not priming or supplying the engine with fuel, check pin 5 for switched voltage. If there’s no voltage at pin 5, check pin 11 and pin 13 for constant voltage from the battery. If your fuel pump is still not working, don’t forget the inertia switch located in the trunk area.

Other known part numbers for the Ford Mustang Constant Control Relay Module are ;

  • F4ZZ12B577A
  • F6SZ12B577AA
  • F8ZF12B581AB
  • F4ZZ12B577A
  • F6SZ12B577AA
  • F8ZF12B581AB
  • F4ZZ12B577A
  • F6SZ12B577AA
  • F8ZF12B581AB

If these pins are showing power and ground and your vehicle continues to have issues, you will need to replace your CCRM. Make sure to consult your sales rep with your VIN number for the proper matching replacement part. This does it for our How To Check Your Ford Mustang CCRM guide, if you have any questions or comments please leave them for us below!


    • Hi John, thanks for reading!

      This part number for a SVT Cobra should still apply, have you unplugged it and compared the pinouts with our CCRM wiring diagram yet sir? Thanks for commenting!

  1. The fuel pump on my 1999 Mustang 3.8 does not appear to be working — The car won’t start even though it turns over fine and I’m getting spark. The battery is almost new. I don’t hear the 2-3 second whirring of the fuel pump when I turn the key to Run. I’m getting voltage at the inertia switch when I turn the key, but it’s only 4.1 volts. Should I be seeing battery voltage? Thanks. Ken

    • Hi Ken, thanks for reading!

      Okay so if I understand correctly, when you turn the ignition to the “ON” position you don’t hear the fuel pump whirr on? Have you checked your fuses? What value are you getting at PIN 13? This should be battery power. Have you tried running a fused power wire straight to the fuel pump, or checking the pump wiring connector in your Mustang if there’s power there?

  2. Thanks for the quick response, John. Yes, when I turn the ignition “ON” I do NOT hear the fuel pump whirr on. Yes, I checked the fuses. No, I did not check PIN 13 of the CCRM. PIN 18 of the CCRM is directly connected to the input of the inertia switch. From your answer, it sounds like I should be getting 12 volts at the inertia switch. Since I’m only getting one-third that amount, would you conclude that either (a) the CCRM is getting reduced voltage from the ignition; or (b) the CCRM has a problem because it is not delivering full voltage to PIN 18? What do you think could cause those problems?

    No, I have not yet tried the power wire or checked the pump wiring connector, but I will.

    Again, I very much appreciate your advice.


    • Hi Ken, yes sorry about that mixup!

      I would suggest checking your fuel pump directly at the harness to make sure you are getting a switched ON signal. This will at least let you know if your fuel pump has died or if it’s a different cause to why your Mustang won’t start

      Let us know how it turns out sir!

      • Hi, 1998 Ford Mustang, need help about how to test the CCRM. A/C compressor clutch not engaging. Already jumped the compressor to the low pressure switch and its starts but the car begins to heat. Need help about running a test. Thank You.

        • Hi Jean, thanks for reading.

          quick question, when you say the car is beginning to heat up, does that mean that the vent air is warm? or the engine temperature is rising?

  3. My 1994 Mustang Cobra, with under 4000 miles, gave me trouble starting which led me to believe the in tank fuel pump was the problem. Once the fuel tank was dropped and the fuel pump removed I found that the pump would run if I put 12v’s to it. Having read your info and others on line I have the following info, key on, pin 5 of the CCRM, no voltage. Pins 11 and 13, just under 12v’s, pin 18 no ground. I have checked all the suggested fuses and the inertia switch, the pump will run if I ground the lead in the EEC test plug. With the above info not sure the next step, replace the CCRM, look else where for the problem? Your comments much appreciated. Ken

    • Hi Ken, thanks for reading.

      When you say the pump runs with 12v put to it, have you checked continuity between the CCRM and the positive fuel pump wire? It could have broke or may have a break in it. I would check there before replacing the CCRM. Thanks for commenting! Let us know how it turns out!

  4. Still working on my fuel pump problem. The pump will operate as I have stated earlier if I ground the fuel pump test lead in the EEC test plug and turn the ignition to run. From what I have read that means that the relay and inertia switch are working as they should. I have not seen any diagram that shows how the EEC test plug is wired to accomplish this or what it is supplying to the fuel pump that is missing under normal conditions. Also, wire colors in the EEC plug don’t match the colors I have seen online. Car is a 1994 Cobra. Ken S.

    • Hi Ken, thanks for reading.

      So couple of quick questions, are you supplying a ground from an external source? meaning not the engine harness? If so have you checked for continuity between the pump and the relay itself?

  5. My 1995 Mustang fans stopped working and according to your CCRM guide, I dont have a power lead to the Low speed cooling fan relay. The only way I get my fans to work is if I turn on the air conditioning fan as well. Please help

    • HI Terry, okay so your fans aren’t working? have you tried to switch your low speed cooling fan relay with your high speed unit? If you do and it doesn’t work the next step is to check the wiring from your CCRM to see if there’s continuity to your relay.

  6. I have a 94 mustang GT 5.0 . IT RAN LIKE new NEVER had a problem, i had taken off my smog pump and replaced it with a pulley wheel. In the process I unplugged the ccrm while the battery was still connected , after I finished installing the pulley wheel and reconnecting the ccrm, I went to crank the car and it wouldn’t crank. I tried connecting a code scanner to read the codes, but it won’t even give a code reading, this never happened before.i could always tread codes up until this.

    • Hi Arthur, thanks for reading.

      Couple of questions. when installing your pulley was your CCRM exposed to water or the harness compromised? When you go to crank the vehicle, do you hear your fuel pump prime? do the accessories and everything turn on? Do you hear a click or nothing at all when you turn the key?

      let us know and we can help! Thanks for commenting!

  7. el sistema theft tiene algo que ver con el modulo ccrm, mi problema es que se funde un fusible y activa el sistema theft, segui el cable y va a dar al modulo ccrm, no se si mi problema sea el modulo o el arnes.

    • Hola Jorge , gracias por comentar

      si el fusible se funde el sistema antirrobo está derritiendo , es probable que tenga una ausencia de tierra o un contacto inadecuado en algún lugar a lo largo de la línea . Me gustaría comprobar todos los motivos y los cables de su arnés a su fusible y asegúrese de que los relés no están recibiendo caliente.

      Utilizamos Google translate para este comentario , es de esperar que funciona. Déjenos saber cómo resulta. Gracias de nuevo.

  8. Entonces mi problema es de Arnés y la solución es buscar alguna imperfección en el cable, muchas gracias por la ayuda

    • Sí me gustaría comprobar a partir de la red de cableado que conduce a la conexión de fusible / relé en sí . Puede haber un corto causando el fusible se queme o motivos que faltan en su motor.

      Mucha suerte y gracias por comentar !

  9. Great article! Very informative, and I can’t wait to utilize this knowledge. My main issue here is I am unable to locate the CCRM. I was told it was in the front passenger side wheelwell, but after looking for a bit, I am unable to find it. What is the best method to find it? Is there a hose or wire I can follow to it from something?

    Thanks again for the article, and for any help I may receive.

    • Hi Jake! Thanks for reading!

      yes I would follow your fenderwell up, it’s best to either jack up the front of the car and use jackstands or remove the fender completely if you are still stuck. It’s above the wheel well splash guard and bolted to the chassis!

  10. found when I drive for a while, park then try to start the car, it won’t start, no sound from fuel pump. an hour or so later, all good and it stars. decided to replace the CCRM. when I unbolted the module, tried to start the car and it didn’t start. I jiggled the module wiring and it started. Replaced the module since I had it out, car would not start. jiggled the wiring and it started. SO I pretty much concluded the wiring harness seems to be the issue. not sure how to fix this though..Any suggestions. seems the problem is up front close to CCRM module connection, as this is where i pressed the wires. (1997 cougar)

    • Hi Brian, breaks in the wiring harness are always the worst. There’s a couple of ways to deal with this issue.

      1. Test continuity between the individual wires using a multimeter
      2. buy a new harness and replace it

      Either one is quite a bit of work, but ideally a new harness is best, especially if you dont want to deal with electric gremlins. Sorry to be the bearer of bad news. Best of luck and let us know how it turns out

  11. Hi John,
    Pulled codes 564 and 332 from my 94 5.0. The CEL goes on after the engine gets to normal temp. If I shut it down, and the immediately restart, then the CEL is off… but returns after a few miles. Is this a CCRM problem? Also, the engine gets really, really hot.
    I don’t know how to use a multimeter yet. Also, the a/c hasn’t worked in years, and I don’t know if the freon is low or pump is bad. Would that cause the codes? Thank you.

    • Hi LRC, thanks for commenting.

      if you aren’t familiar with how to use a multimeter, you can pick up a cheap voltage light which should help at least determine ground and voltage.

      When you say the engine gets hot, how hot is hot? are both radiator hoses hot? or is only the one from your radiator hot? in other words is your thermostat opening?

      As far as the AC, I would check to make sure your AC compressor is kicking in first. As far as the 564 and 332 codes go, go through this guide to check your Mustang CCRM. Best of luck to you!