Help Please

OK, let's get some more information. Test CCRM pin #14 (DB) and #17 (LG/R) with the CCRM clicking. These are the signal leads that control the low speed and high speed fan. Need to know what they are doing.

We may also need to Ohm these signal return lines back to PCM pin #45 and #46. We want to look for a short to ground or a short to VPWR. Might also be a good idea to test for a short between the wires. I could see how that could really confuse the CCRM.

Have you done a visual inspection of the car's wiring harness? Looking for evidence of physical damage or rodent activity?

Are you absolutely POSITIVE:

• This is the CORRECT CCRM for the application? There are differences in the CCRM as well as slight differences across the model years.
• There is absolutely no signs of heat damage at the CCRM connector? I have helped more than one person where the problem turned out to be pushed/melted/shorted pins at the CCRM.

Did you confirmed that the signal return lines were not shorted to each other or shorted to ground?

Refresh my memory. Have you CONFIRMED the CCRM grounds with a voltage drop test all the way back to battery negative with the CCRM clicking.

EDIT: the more I think about this I believe there's short to ground in CCRM pin #17. A voltage reading of zero indicates that high speed cooling fan is being called for. However at initial key on, the cooling fan should be off. That means zero volts on pin #14 and 12 volts on pin #17.

Please double check your work paying special attention looking for a short to ground in the high speed cooling fan circuit.

One way to test this theory is to un-pin CCRM pin #17 and see if this stops the CCRM clicking. This will disable the high speed fan but won't prevent the motor from starting.

Are you saying progress is being made? It stopped the CCRM clicking to de-pin #17. WOW! Give yourself a big pat on the back for sticking with all the testing. Looks like the work is starting to pay off.

But it sure seems to me there are other shorts in the harness.

Are all of the fuel injectors pulsing?

Do you have ODB2 data graphing? Would be handy to know the MAF and Long term fuel trims (LTFT).

Jim5208 said:

Checked injector firing....5, 6, 7 and 8 no injectors 1,2,3 and 4 yes

Click to expand...

Here's an important detail about injectors 5-8 that you may not be aware of. The injectors in question are on the left side of the motor. There's a portion of the engine wiring harness that crosses from the right side to the left side. It's located towards the rear of the motor behind the throttle body. This part of the wiring harness lays over a few brackets and such associated with the EGR system. This is important:

• The EGR system is hot
• The location is such that it's not easily seen or accessed.
• there are brackets with sharp edges that over time can abrade the harness. Further since the brackets are metal it offers a quick path to ground.

I have helped a few people where this turned out to be where the problem was located. Now it also seems to me that there may be more than one problem going on here.

Have you also inspected the large square main motor wiring harness connector on the back right of the engine bay. And by "inspected" I mean:

• Take it apart.
• Perform a thorough visual inspection inside and out. Look for evidence of over heating or corrosion.
• Clean with electrical contact cleaner.
• Dry with compressed air.
• Finally re-grease the pins with di-electric grease.

We may need to go over the method used to Ohm out the signal return line. It appears that there is a short to ground but the previous Ohm testing did not discover it. Having a reliable method to test is important because it offers a way to locate a short within the harness. Consider if the meter has an beep alarm. Place the VOM on the wire path to be tested. Working down the wiring harness grab and wiggle the harness while monitoring the VOM for a change. Many times this will pinpoint the location of the break/short.

Jim5208 said:

I have taken motor wiring harness apart no problems. Ohmed all returns wiggling all wires all 0.5 ohms or less. With all injector connectors plugged in, I than get readings on returns other than the one I'm ohming. This does not make any sense to me. If all were connected to one wire like the power wire than I could see that happening.

Click to expand...

Well.................

On the surface that would imply that the signal return lines are shorted to each other. Or the circuit being tested was not electrically isolated at the time. For an Ohm tester to work correctly the circuit needs to be isolated. Otherwise the VOM will read the other loads.

The injectors are ground start devices. Which means the PCM "fires" the device by grounding the signal return line. IF two signal return lines are shorted to each other, that means when the PCM fires one device it will fire BOTH.

IMO the only way to avoid a wild goose chase is to repeat the test but in a very precise way. That way I know positively what you are doing and we are both on the same game page.

• Remove the battery negative and positive.
• remove the connector for injector 5-8
• remove the connector at the PCM.
• let's start with injector #5. Using a back probe T-pin put one lead of the VOM on the signal return T/BK (not red).
• At the PCM the #5 injector return is pin 73. You will know that you have the correct pin if it's the same wire color.
• Measure and record the Ohm resistance.
• Here's the important part. Check the resistance of all OTHER pins at the PCM (other lead still connected at the injector). Because the devices have been disconnected on both ends (isolated circuit), all of the other PCM pins should read OPEN. Record the pin numbers of any pin not testing open.
• Also test from the injector return to a known good ground. With nothing connected on either end this should read open as well.
• finally test to battery positive (not the battery itself but the disconnected positive terminal).

Want more proof? The CCRM high speed fan pin #17 (LG/P) should still be un-pined from previous tests. This should go to PCM pin #46. With both ends of the circuit disconnected this signal return should read open when tested to ground or power. But should read low Ohms at the PCM.

Note of caution. When probing connectors be careful not to spread the connector such that it no longer fits tightly. Don't force too large of a probe into the connector.

I'm somewhat confused by some of your descriptions of how you are performing the Ohm test. To confirm that you Ohm'ed the injector returns all the way to the PCM right? Performing the test with the main engine plug undone doesn't test the wire path all the way back to the PCM.

Ohm tests are often the first tests used because they are straight forward and easy to understand. IMO it might also be important to understand the limitations of the test methods currently being used. Ohm tests don't always find every kind of wiring harness fault. Remember one of the conditions of an Ohm test is for the circuit to be inactive. However the circuits is not used that way. It is used with current flow occurring in many different circuits.

I'm a big believer in Occam's Razor. Occam's Razor would have us to look for a straight forward cause to this problem. I'm sure once the problem is found it will make sense.

https://en.wikipedia.org/wiki/Occam's_razor

Many times when I work on a serious head scratching problem that simply doesn't make sense I find it helpful to stop and reset. Go back and double check some of the BASE assumptions that started the trouble shooting session. I'm assuming that you bought the car with it's current problems. So some parts of the car's history are unknown. Recheck everything. Take nothing for granted.

For example. I remember helping someone with a wiring problem that made it appear the entire car's wiring was F'ed up. To make a long story short the problem turned out to be two similar large connectors were installed backwards.

I have also helped people with electrical problems caused by mixing and matching wiring harness parts from different model year Mustangs. Not realizing that Ford uses the same connectors that LOOK the same but how they are wired are very different.

We know for a fact there's a ground on CCRM pin #17 but the wire path tests good right? Where is that ground coming from? IF the signal return is not grounded external to the PCM then the ground has to be coming from the PCM right? What might cause this on two PCM's?

Just trying to think outside of the box. What if the wrong PCM has been used by the prior owner? And when looking for a replacement you matched the numbers on the PCM installed thus installing another incorrect PCM?

Another possible theory is there's some external problem in the wiring harness such that it shorts out the PCM when turned on. The new PCM suffers the same fate as the original. Have you inspected the printed circuit board of the new PCM looking for evidence of heat damage?

Unless you can find an evidence of other work done/swapped/repaired on this car you may be in for a long row to hoe. It may be necessary to test virtually all of the signal lines back to the PCM. In addition to testing the wire path you should also double check that the pin outs and wiring colors match the Ford Wiring diagrams. Again. Take nothing at face value.

I think it's official. You have a real puzzler on your hand here.