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wmburns
SN Certified Technician
I have to admit to being confused by some of your replies. It's not clear to me the reported units of measure (volts or Ohms) and HOW the measurement was taken (IE from which point to which point). Remember that you are taking the readings and know what you are doing. I'm not there to see it and can only rely on what you put into the thread. Asking me to guess risks going on a wild goose chase.
For a ground wire pathway, 0.8 Ohms is still seems on the high side. If this is too high or not depends upon the size of the load. On the other hand a voltage drop ground test 0.8 volt is EXCESSIVELY high (0.250 volt limit).
But given that you appear to not be able to pick up any injector return lines at the PCM and suspect a wiring problem, I would look at the large C104 connector in the engine bay. Take it apart. Clean both sides with electric contact cleaner. Dry with compressed air. Put a small amount of di-electric grease in each of the female pin holes. Don't put too much as hydrolocking could occur.
As for the signal return lines the usual way to perform this test is to disconnect the device on both ends and then measure the resistance between the return wire and a known good ground. This should be a very high (open) Ohm reading. Next use a scrap piece of wire to extend one VOM lead measure the resistance through the signal return wire. This should be low. This is where having a set of wring diagrams comes in handy to find the wire colors and connector pin outs.
Another good piece of information to have is the voltage measurement between the injector RETURN side and a known good ground with the motor cranking. We should see 12 volts when the injector is open and low voltage when the injector is commanded closed. I would like to compare these readings between a working and non working injector. As a reminder the wire on the supply side should be a solid and constant 12 volts.
It also seems silly to me to ignore the clicking CCRM. It would be handy to know which relay inside the CCRM is clicking. With the CCRM clicking try reading the voltage between the following wires and a known good ground. What we want to know is if the voltage is coming/going with the clicks.
To confirm that you have inspected:
For a ground wire pathway, 0.8 Ohms is still seems on the high side. If this is too high or not depends upon the size of the load. On the other hand a voltage drop ground test 0.8 volt is EXCESSIVELY high (0.250 volt limit).
But given that you appear to not be able to pick up any injector return lines at the PCM and suspect a wiring problem, I would look at the large C104 connector in the engine bay. Take it apart. Clean both sides with electric contact cleaner. Dry with compressed air. Put a small amount of di-electric grease in each of the female pin holes. Don't put too much as hydrolocking could occur.
As for the signal return lines the usual way to perform this test is to disconnect the device on both ends and then measure the resistance between the return wire and a known good ground. This should be a very high (open) Ohm reading. Next use a scrap piece of wire to extend one VOM lead measure the resistance through the signal return wire. This should be low. This is where having a set of wring diagrams comes in handy to find the wire colors and connector pin outs.
Another good piece of information to have is the voltage measurement between the injector RETURN side and a known good ground with the motor cranking. We should see 12 volts when the injector is open and low voltage when the injector is commanded closed. I would like to compare these readings between a working and non working injector. As a reminder the wire on the supply side should be a solid and constant 12 volts.
It also seems silly to me to ignore the clicking CCRM. It would be handy to know which relay inside the CCRM is clicking. With the CCRM clicking try reading the voltage between the following wires and a known good ground. What we want to know is if the voltage is coming/going with the clicks.
- cooling fan low speed - pin #1 R/O
- cooling fan high speed - pin #6 O/LB
- fuel pump - pin #5 DG/Y
- PCM power - pin #24 R
- AC clutch - pin #23 BK/Y
To confirm that you have inspected:
- the grounds around the radiator core support and they are clean and tight.
- The black wire with white stripe that goes around the battery to a single pin connector. CONFIRM that it is clean and tight.
- The motor grounding strap from the left hand motor mount to the frame rail. This strap is normally visible near the oil filter.
- That you have perform the alternator voltage drop test on the positive and negative lines and it is less than 0.250 volts with the key on.
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Going back to the single round pin connecter by the battery. It's a black wire, that's the female end. Im getting 1.1 ohms connected to a good known ground. The male end is white with a red strip. I'm getting 0.0 ohms on it. There's a 2 pin connecter beside it. It has a black/white and a Black/yellow. Ones wire goes to battery ground and the other is going to radiator support. The black/white, it seems to be the one going to the ground connecter under the air breather. I'm getting 0.8 ohms on that wire. This is all being done with positive unhooked from battery.
wmburns
SN Certified Technician
I think we may have a disconnect here. It seems to me that you are measuring the ground resistance AWAY from battery negative (or said in another way this is a ground loop). This isn't really giving any useful information. Once the connector near the battery is split taking any measurements away from the battery will also read the resistance of the device at the far end (ground loop). That's likely why you are seeing resistance values so high.
The resistance measurements need to be taken from the device TOWARDS battery negative.
For proof reconnect everything and then go to the ground at the air breather. Now take the resistance measurement with one lead on the battery negative and the other lead on the ground being tested. Pay close attention to any ground reading more than 1 Ohm unless the circuit is known to be a high amp circuit.
The resistance measurements need to be taken from the device TOWARDS battery negative.
For proof reconnect everything and then go to the ground at the air breather. Now take the resistance measurement with one lead on the battery negative and the other lead on the ground being tested. Pay close attention to any ground reading more than 1 Ohm unless the circuit is known to be a high amp circuit.
wmburns
SN Certified Technician
A fractional Ohm for a pilot duty circuit is fine. Likely we can rule out a bad CCRM ground as the "cause" of the CCRM clicking.
But there are other "possible" causes. What about the rest of the tests requested?
I've verified 12v at each injector. Ive unplugged the connecter on right side checked ohms on all power wires, pins 38 an 39 are the pins that all power wires ohm to, Pin 9 must be supply power to the injectors, they all ohmed to it also.
Ohmed the wires on all injectors I believe would be the injectors pulse. They all ohmed to correct pins. inj 1 1.3 ohms inj 2 1.2 ohms. inj 3 1.3 ohms, inj 4 1.6 ohms, Inj 5 0.9 ohms, inj 6 0.6 ohms, inj 7 0.8 ohms, inj 8 0.9 ohms. This is being done from the connecter on right side to each injector.
Ohmed the wires on all injectors I believe would be the injectors pulse. They all ohmed to correct pins. inj 1 1.3 ohms inj 2 1.2 ohms. inj 3 1.3 ohms, inj 4 1.6 ohms, Inj 5 0.9 ohms, inj 6 0.6 ohms, inj 7 0.8 ohms, inj 8 0.9 ohms. This is being done from the connecter on right side to each injector.
With key on fan running relays clicking in ccrm, I've got pulsating at all drivers side injectors. No pulsating on passenger side, the only way I can get passengers side to pulsate is unplug #4 than 1 2 and 3 will pulsate. If I unplug 1 2 or 3 they have power but no pulsating. #4 will have power if I unplug 1 2 or 3.
wmburns
SN Certified Technician
Back in post #25 I asked for some voltage measurements at the CCRM. The CCRM is a relay that controls power to many of the car's systems. It would be EXPECTED to not have power down stream of the CCRM IF the CCRM's relays are not latching (the clicking!).
Based upon the information in this thread IMO it's a waste of time to perform additional trouble shooting until it has been CONFIRMED that the CCRM is working correctly.
Based upon the information in this thread IMO it's a waste of time to perform additional trouble shooting until it has been CONFIRMED that the CCRM is working correctly.
I ordered a brand new ccrm, came in today. Still the same problem. The pats has not been programmed yet. There was no changes with new pcm. Plugged in new pcm ran for a few minutes than stopped, doing the same thing as before. With key on ccrm clicking Pin 1 has 8.6 volts pin 6 has 6.8 volts. I can unplug one injector readings switch. Pin 5 has 12.8 volts. Pin 24 has 12.8 volts pin 23 has 0 volts
wmburns
SN Certified Technician
So that we are on the same game page, you have taken resistance measurements on all of the fuel injectors and they are close to each other. Right?
Based upon your last post the CCRM relays that are "clicking" are for the cooling fan. The Mustang uses a "fail safe" circuit for the cooling fan. That is the CCRM needs a signal from the PCM to stop the cooling fan. IF this signal is missing, then then cooling fan runs.
What I'm looking to rule out is IF the PCM is coming and going. And each time that it does the CCRM cooling fan relay clicks.
What are some things that could cause the PCM (more than one) to come/go? Well since we have confirmed a SOLID 12 volts at the CCRM pin #24 (PCM power feed), that leaves:
Next since we can change the symptom by unplugging injectors let's rule out the Excessive power draw theory. Let's disconnect:
IF not, then we need to plug back in the sensors one at a time to see if the symptom changes. This will tell us which sensor is the offending sensor.
Based upon your last post the CCRM relays that are "clicking" are for the cooling fan. The Mustang uses a "fail safe" circuit for the cooling fan. That is the CCRM needs a signal from the PCM to stop the cooling fan. IF this signal is missing, then then cooling fan runs.
What I'm looking to rule out is IF the PCM is coming and going. And each time that it does the CCRM cooling fan relay clicks.
What are some things that could cause the PCM (more than one) to come/go? Well since we have confirmed a SOLID 12 volts at the CCRM pin #24 (PCM power feed), that leaves:
- bad PCM ground
- loose connection at the PCM
- Excessive power draw causing the PCM to kick out on a thermal
- going to assume that the PCM is good since this same symptom has occurred on more than one PCM.
- the Black wires with the white stripe (G104) PCM Pins 24, 51, 76, 77,103
- the all black wires (G201) PCM pins 25
- PCM (G201), pin #33 (PK/O)
Next since we can change the symptom by unplugging injectors let's rule out the Excessive power draw theory. Let's disconnect:
- All 4 O2 sensors.
- MAF
- both coil packs.
- IAC
- DPFE
- Cooling fan
- all (8) injectors.
- EVAP purge flow sensor
- IF automatic the large electrical connector on the transmission DTR shifter control.
IF not, then we need to plug back in the sensors one at a time to see if the symptom changes. This will tell us which sensor is the offending sensor.
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