2013 Ford Explorer A/C Electronics diagnostics

2013 Ford Explorer 3.5L TiVCT. Air conditioning is inoperable. Codes present are:
P0532 A/C pressure sensor “A” Circuit Low.
P0642 Sensor reference voltage A circuit low
This is a 3 wire sensor-SIGRTN, VREF, ACPT.

The A/C system pressure is fine on the manifold set, but on the scanner the PID is reading 0 PSI. The Sensor voltage is 0 as well. I can manually turn on the compressor from the special functions menu on the scanner. I had a shop tell me to replace the sensor. No luck. Same issue.

I went to the wiring schematic on All Data and was messing around under the hood with the wire harness looking for a damaged/loose wire connection. Closed the hood for the night and the next day when I started the vehicle, the A/C worked as normal. Ran fine for 3 weeks and now the same issue has occurred again. This time I am not able to get the system on again by messing with the harness. I believe my problem is either going to be a open or a short in either the PCM or one of the 3 sensor wires. I do not want to damage the PCM, so I would appreciate any thoughts, or instruction on how to properly locate the issue.

I think your first move needs to be voltage checks at the ACP itself. Key on, unplug the sensor and check voltage on all three pins. Try not to disturb the rest of the harness while doing this, as you may inadvertently make the problem go away again. :silly:

This will confirm if the ACP sensor VREF is truly low during your testing. Exactly how low it is can also give us some clues. VREF all the way at zero would suggest a dead short. VREF somewhere between 0V and 5V would suggest a resistive short.

Thanks for the reply Tyler. I checked the three pins harness side with the KOEO.
VREF = 0.572 V, ACPT = 25.8 mV, SIGRTN = 27.6 mV. I attempted to upload the schematics as a pdf with my original post but it does not appear to have worked. I will try again here.

Rich G wrote:

Thanks for the reply Tyler. I checked the three pins harness side with the KOEO. VREF = 0.572 V, ACPT = 25.8 mV, SIGRTN = 27.6 mV.

Excellent. That means it's broken right now. DON'T TOUCH ANYTHING.

Unfortunately, the AllData diagrams aren't attaching right? I snipped a bit of the OE diagram for reference:



Obviously, I'm sure that the VREF goes to more places than just the ACP sensor and the Generator Current Sensor. But given that they both share the same source wire at the PCM, I'd suggest going after the Generator Current Sensor first.

It lives somewhere in this area:



As carefully as reasonably possible, I'd suggest watching the VREF voltage on your meter while reaching down and unplugging the Generator Current Sensor. If your VREF immediately jumps up to five, you're on the right track.

Thank you Tyler. I'm definitely on the right track. I did as you said and unplugged the Generator current sensor. Voltage on the meter for the ACP sensor immediately went to 5.1 V. Plugged everything back except the gen sensor and A/C works great. Crazy thing now is my Generator is not charging the battery and I am getting the code P0625 "Generator Field F Terminal Circuit Low". I verified this to be correct with the multimeter. Battery voltage is 11.6V with the vehicle running. I will have a new sensor in the morning, and now it looks like I may also have a new Generator to purchase. To be honest, I am a little skeptical that I have a bad generator and a bad sensor I don’t see where these 2 are hard connected to each other Could it be the Generator was the issue all along and the sensor was just relaying the info to the PCM and therefore as a result the PCM cut the ACP?

Thank you Tyler. I'm definitely on the right track. I did as you said and unplugged the Generator current sensor. Voltage on the meter for the ACP sensor immediately went to 5.1 V. Plugged everything back except the gen sensor and A/C works great.

Perfect. Unless you saw coolant, water or excessive corrosion inside the GCS itself, then I'd say that sensor is internally shorting the VREF to ground.

To be honest, I am a little skeptical that I have a bad generator and a bad sensor I don’t see where these 2 are hard connected to each other Could it be the Generator was the issue all along and the sensor was just relaying the info to the PCM and therefore as a result the PCM cut the ACP?

Eh, I really doubt this is an alternator problem. Even if the alternator had failed or was falsely reporting, it still wouldn't cause a the GCS to short the VREF to ground. You'd get other faults/symptoms.

I say stick to the original plan and replace the GCS first. Clear faults and retest for charging system voltage and A/C operation.

Some new info to share. When I unplug the generator current sensor, the alternator output is at 14.5V. I will replace the sensor in the morning and update with progress. Thank you again for your knowledge and willingness to help.

Tyler, I just wanted to update on the issue you have been so gracious to help with. The replacement sensor did the job. No more PCM DTC codes and A/C is blowing cold and the alternator is charging. My next job is to tackle the ABS/traction control codes LOL. I am pretty sure it's the ABS module that needs replaced on that one. But I will definitely be posting if I can't figure it out. I can't thank you enough for your help man. You saved me a lot of head ache and $$. Have a great weekend!!

Awesome! Thanks for getting back to us with the fix! This kind of follow-up is what really benefits us as a community.

For my info, how much fun was it to change the current sensor? What brand of sensor did you use?

Please feel free to start a new thread on your ABS problem whenever you're ready.

It was a piece of cake to change. Easily accessible. The sensor is 6"off the alternator and just tapes to the Bat+ cable. It was a 20 minute job. The hardest part was getting my big hands between the fan shroud and the engine to wrap electrical tape and make sure the sensor is located in the same spot as the old one. I am usually a strict Motorcraft guy but the did not have the part and could not get the part that day plus it was $73.00. I ended up installing a "Standard Motor Products" sensor from Oreilly's (Part number BSC9). They originally told me they did not have it, but then were able to locate it by cross referencing the FoMoCo (Part number BT4Z-14B357- I gave them. The sensor cost me $23.00.

Thank you again brother and I am so grateful for your help. I will certainly start a new thread when I dig into the ABS system.

I have a 2011 Ford Explorer that was having the exact same issue. I followed the checks listed and it was also the Current sensor that was bad pulling down the Vref, causing the AC pressure sensor to have 0 volts on the scanner. What was strange is prior to this the AC pressure sensor would display correctly then fall to 0 volts intermittently. I am so thankful to have read this post as you have saved me so much time getting this finally fixed!