Ford 500 Repair Question
Bad Computer, CCRM, or something else
I am hoping you may be able to help me. I am having an
intermittent check engine light. I purcahsed a code scanner and scanned
the computer. It says the mass airflow sensor is bad. I replaced the sensor
and it is still telling me it is bad. It is also telling
me that the fuel pump is bad. I have no starting problems, the car
starts up the first time everytime and does not hesitate during operation and
because of the mass airflow sensor issue I doubt the fuel pump is bad.
I also disconnected the mass airflow sensor and test drove it to see if
I noticed any performance problems and did. So I know the mass airflow sensor
thats on there is good.
I've reset the computer probably a dozen times. I've unplugged the battery and let
it sit for at least five minutes and then hook it back up. I then
drive the car for about five minutes and the check engine light
comes back on, however it does not stay on. It comes on and goes off.
I've also looked over the Haynes wiring schematic section for this vehicle.
The Massairflow sensor, fuel pump, and all of the EGR sensors are connected to
one another via the CCRM. So I am wondering if its possible that one
of the EGR sensors could be malfunctioning and causing the massairflow to cut on and cut off and for
whatever reason the computer is not putting out an error code for that sensor.
I've also had people suggest that the computer could be bad. Before I start replacing
the sensors I'd like to get a general idea of where or which one it is that
might be bad. Some of these sensors cost more then a used computer and
I don't want to have to start replacing them if I don't have to. I am also
wondering if it is possible that the computer could be bad.
The massairflow sensor is also connected to the CCRM, so I am wondering if
the Constant Control Relay Modual (CCRM) may be bad, but everyone
I have talked to all say no, that it does not control
or have anything to do with the Mass Airflow sensor but only the air
conditioning and the electric radiator fan. However on the wiring schematic
its dammn near connected to everything. So if it was going bad I don't understand why
it could not cause the problems I'm having, unless my Haynes wiring schematic is wrong.
I know from research of other vehicles the CCRM can cause problems simular to what I am having.
The A/C also does not work, which is plugged into the CCRM, but the A/C could just be a recharge issue.
The electric fan does work, which is why everyone says there is nothing wrong with the CCRM.
If the CCRM is bad, exactly where is it located and will I be able to find a part number for it because every place I have checked all tell me they don't know what I am talking about or they can't find a distributor that supplies it. Even some junk yards I've called have no idea what I am talking about when I say CCRM, or Constant Control Relay Modual. Also is it possible the name changed cause I've had that problem with a couple of parts on this car.
Oh also, I forgot to mention, I disassembled the entire intake system from the fender wall to the mass airflow sensor to look for any possible obstructions/debris that may have gotten sucked into it before it reached the filter. I did this just incase something (plastic bag, etc) was obstructing the airflow enough to cause the sensor to go off. I found nothing. The airfilter is new and is a regular ford motor craft airfilter.
I strongly feel its the CCRM causing the problem, but I'm not sure. I could be wrong because everyone around town is saying no. I've never had this problem before.
I don't really have an answer for your intermittent check engine problem but I would like to clarify a few things that might help. First, when the light comes on, it should set a trouble code, which you had scanned for initially. The light keeps coming on and going off. Is it setting the same codes every time? Or, did you only have it scanned the first time. Have it scanned again if you didn't, and report back codes. I'm not an expert on the CCRM, but I'd like to explain it better. The CCRM is a relay module or relay center as it's called on other vehicles, but the CCRMis a sealed unit that's not easily accessable. There are a few wires connecting the PCM (computer) to it but basically there are some relays for the cooling fan, AC clutch and fuel pump. The PCM controls these relays to go on and off. I don't think you have a problem with the CCRM, unless the AC relay is bad and that's a problem for another time. The individual relays can go bad, but your fuel pump and cooling fan work so I would forget about the CCRM being bad except possibly for the AC relay. The Mass Air Flow Sensor is wired to the computer, not the CCRM. If you look at the wiring diagram, it has 4 wires, red which is reference voltage from the PCM, black/lt.green which is ground, and a tan/lt.blue and a lt.blue/red which go back to the PCM. The codes you got initially for the MAF and Fuel Pump circuit do not mean the MAF sensor or fuel pump are bad. The code for the MAF can be caused by other things like an air leak and the code for the fuel pump is for the circuit, not necessarily the pump. So check for trouble codes again and report back what they are or if any codes show up at all. The engine seems to be running OK so the check engine light might be a problem with the computer, a wiring problem, an old spark plug wire that needs to be replaced or some other minor thing that clears itself and shows up again . Don't start replacing things without more troubleshooting starting with another scan. I was trying to explain things so you could understand it better.
Anyone else can jump in with their thoughts on the light going on and off.
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The Codes im getting are 543 and 76. Also today I got a new code, code 57. I never got this code before, its brand new. However, I never done a code check after I drove the car without the MAF connected, so I don't know if its related.
With the exception of the new code today, everytime the other codes come on I'm getting the same error codes.
In regards to the spark plugs, I had the spark plugs, distributor cap and wires changed. I took it into a locale professional shop and had it done there because I could not get my hands between the engine and fire wall to reach the plugs.
I was wondering if it could be a vaccum leak because I did have to replace a vaccum hose about a month ago. There may still be other breaks or leaks in the system somewhere.
Also my cruise control malfunctions every so offten. It will engage and disengage on its own and the vehicale will accelerate, then fall back.
I also had an issue about two months ago when I was exiting the freeway. The cruise control suddenly engaged and the vehicle started accelerating on the off ramp. The cruise control was still on, just not activated. When it re-engaged, it had been disengaged because I had started stopping.
From everything I have read and from what people have told me, the cruise control is tied into the vaccum system, so theres a strong possibility that the vaccum system is causing the cruise control problem. The cruise control also malfunctions more frequently when it rains. The check engine light comes and goes no matter what time of the day or what the weather conditions are.
If it is a vaccum leak I'm wondering if anyone might be able to direct me to a website with a complete diagram/schematic of the hoses. The repair manual I have has very little information about the vaccum system.
I tried checking for a leak using brake cleaner. The guys at advance auto told me to spray it on the connections while the vehicle is running, and if there is a leak anywhere the engine should surge. It never surged.
The criuse control does run off of vacuum. I can't find vacuum hose diagrams showing the cruise control system. Check all of the vacuum system hoses and connectors for damage, splitting etc. The cuise control module is mounted by the driver side strut tower. It's round with a large vacuum hose and smaller hoses. You need to do a very thorough check of all the hoses and connections. Or you could buy a hand operated vacuum pump and disconnet hoses one at a time, plug one end and apply vacuum and see if it holds. You might want to check around the throttle body and intake manifold. With the engine running use a small propane bottle and with it opened to a slow flow, go around the throttle body and manifold. If there is a leak the engine will rev slightly higher.
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Ok, im prety sure I know where the cruise control module is. I've found it before, the first time I was looking for a leak. Apparantly I may not have checked throughly enough. I'll give it a try and see what happens.