P0532-00, No A/C with flashing snowflake

[DaRosa218]

Hey guys,

So I bought the Yukon with the A/C system not working (hence how I got a great deal) and figured it would be an easy fix as it had no Freon in the system.

I had A/C system charged at a shop and the tech advised me that I probably need to have the BCM re-flashed. Never heard of it having to be reflashed but could still be a part of the problem.

I have a foxwell Tech 2 scanner and came up with the following DTC's that are causing the A/C system to not activate.

P0532-00 Refrigerant Pressure Sensor Circuit Low Voltage

AC Permission- Withheld

AC Head Pressure Out of range.

I have so far replaced the Low Pressure & High Pressure switch and even tried the old jumper wire trick on the Low Pressure switch to see if I could jump the compressor with no luck.

I am lost where to go from here, I verified the pressure compared to my Brothers Silverado with his AC off like mine and adjusted to his pressure settings.

Any help would be greatly appreciated as it is starting to warm up in California.

 

[Kraig]

Check the sensor for 5V and ground at the appropriate pins and if it’s there, check for the signal out. I’m guessing it probably goes to the BCM, but I might be wrong

 

[Moose912]

Never heard of bcm issue either. What brand sensors did you use? If the snowflake flashes it recognizes an issue and prevents the system from coming on. If you can’t jump compressor on it could be as simple as a dead compressor. Not super likely on these trucks however. I’ve seen more climate control units go out than compressors on these.

 

[thompsoj22]

Hey guys,

So I bought the Yukon with the A/C system not working (hence how I got a great deal) and figured it would be an easy fix as it had no Freon in the system.

I had A/C system charged at a shop and the tech advised me that I probably need to have the BCM re-flashed. Never heard of it having to be reflashed but could still be a part of the problem.

I have a foxwell Tech 2 scanner and came up with the following DTC's that are causing the A/C system to not activate.

P0532-00 Refrigerant Pressure Sensor Circuit Low Voltage

AC Permission- Withheld

AC Head Pressure Out of range.

I have so far replaced the Low Pressure & High Pressure switch and even tried the old jumper wire trick on the Low Pressure switch to see if I could jump the compressor with no luck.

I am lost where to go from here, I verified the pressure compared to my Brothers Silverado with his AC off like mine and adjusted to his pressure settings.

Any help would be greatly appreciated as it is starting to warm up in California.

View attachment 222138 View attachment 222139 View attachment 222140 View attachment 222141

Thanks for the pic's in regard to using the tech2. I recently got the vertronix knock off and need to build knowledge with how to use it. I think i would advise an alldata subscription, your tech2 is defining the problem and you now need to follow a troubleshooting tree that would be outlined in a factory service manual and you will have it fixed in no time! The TS tree will designate which component to check, how to check it and likely replacement part. your allmost there.

 

[DaRosa218]

Thanks for the pic's in regard to using the tech2. I recently got the vertronix knock off and need to build knowledge with how to use it. I think i would advise an alldata subscription, your tech2 is defining the problem and you now need to follow a troubleshooting tree that would be outlined in a factory service manual and you will have it fixed in no time! The TS tree will designate which component to check, how to check it and likely replacement part. your allmost there.

Thanks, I will look into that! It's been pouring rain out here and been working a lot lately so I haven't been able to diagnose more on it

 

[SPDMETL]

If you haven't got this working yet, check the lines that go to the rear A/C...I've just read several threads where there was perforation near the RR wheel

 

[DaRosa218]

Sorry, work has been outrageously busy lately. I was able to get the A/C going by jumping the A/C compressor relay. I am going to continue to look into why there is no signal to engage the compressor, but at least it works for now in this 100+ degree Central California weather.

 

[swathdiver]

From the shop manual:

DTC P0532 = Air Conditioning A/C Refrigerant Pressure Sensor Circuit Low Voltage

Circuit/System Description

The engine control module (ECM) monitors the high side refrigerant pressure through the A/C refrigerant
pressure sensor. The ECM supplies a 5-volt reference and a low reference to the sensor. Changes in the A/C
refrigerant pressure cause the sensor signal to the ECM to vary. When the pressure is high, the signal voltage is
high. When the pressure is low, the signal voltage is low. When pressure is high, the ECM commands the
cooling fans on. When pressure is too high or too low, the ECM will not allow the A/C compressor clutch to
engage.

Conditions for Running the DTC

 Engine is running.
 Any of the conditions for setting the DTC are met for 15 seconds.
 Battery voltage is between 11-18 volts.

Conditions for Setting the DTC

 The ECM detects that the A/C pressure is less than 1 psi (0.01 volt) sets DTC P0532.
 The ECM detects that the A/C pressure is more than 428 psi (4.92 volts) sets DTC P0533.

Action Taken When the DTC Sets

 The ECM will not illuminate the malfunction indicator lamp (MIL).
 The ECM stores the Failure Records.
 The A/C compressor clutch is disabled.

Circuit/System Verification

Ignition ON, observe the scan tool A/C Pressure Sensor parameter. The reading should be between 0.1 volts (1
psi) and 4.90 volts (425 psi) and change with A/C refrigerant pressure changes.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the A/C refrigerant pressure sensor.
2. Ignition OFF, test for less than 10 ohms between the low reference circuit terminal 1 and ground.
 If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 2 and ground.
 If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
 If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.
4. Verify the scan tool A/C High Side Pressure Sensor parameter is less than 0.1 volts (1 psi).
 If greater than the specified range, test the signal circuit terminal 3 for a short to voltage. If the circuit tests normal, replace the ECM.
5. Install a 3A fused jumper wire between the signal circuit terminal 3 and the 5-volt reference circuit terminal 2. Verify the scan tool A/C High Side Pressure Sensor parameter is greater than 4.90 volts (425 psi).
 If less than the specified range, test the signal circuit for short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
6. If all circuits test normal, test or replace the A/C refrigerant pressure sensor.

 

[DaRosa218]

From the shop manual:

DTC P0532 = Air Conditioning A/C Refrigerant Pressure Sensor Circuit Low Voltage

Circuit/System Description

The engine control module (ECM) monitors the high side refrigerant pressure through the A/C refrigerant
pressure sensor. The ECM supplies a 5-volt reference and a low reference to the sensor. Changes in the A/C
refrigerant pressure cause the sensor signal to the ECM to vary. When the pressure is high, the signal voltage is
high. When the pressure is low, the signal voltage is low. When pressure is high, the ECM commands the
cooling fans on. When pressure is too high or too low, the ECM will not allow the A/C compressor clutch to
engage.

Conditions for Running the DTC

 Engine is running.
 Any of the conditions for setting the DTC are met for 15 seconds.
 Battery voltage is between 11-18 volts.

Conditions for Setting the DTC

 The ECM detects that the A/C pressure is less than 1 psi (0.01 volt) sets DTC P0532.
 The ECM detects that the A/C pressure is more than 428 psi (4.92 volts) sets DTC P0533.

Action Taken When the DTC Sets

 The ECM will not illuminate the malfunction indicator lamp (MIL).
 The ECM stores the Failure Records.
 The A/C compressor clutch is disabled.

Circuit/System Verification

Ignition ON, observe the scan tool A/C Pressure Sensor parameter. The reading should be between 0.1 volts (1
psi) and 4.90 volts (425 psi) and change with A/C refrigerant pressure changes.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the A/C refrigerant pressure sensor.
2. Ignition OFF, test for less than 10 ohms between the low reference circuit terminal 1 and ground.
 If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 2 and ground.
 If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
 If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.
4. Verify the scan tool A/C High Side Pressure Sensor parameter is less than 0.1 volts (1 psi).
 If greater than the specified range, test the signal circuit terminal 3 for a short to voltage. If the circuit tests normal, replace the ECM.
5. Install a 3A fused jumper wire between the signal circuit terminal 3 and the 5-volt reference circuit terminal 2. Verify the scan tool A/C High Side Pressure Sensor parameter is greater than 4.90 volts (425 psi).
 If less than the specified range, test the signal circuit for short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
6. If all circuits test normal, test or replace the A/C refrigerant pressure sensor.

Thank you for the reply, I just replaced both High and Low pressure sensors. I will test the ohms and voltage as stated and see if there is a wiring issue somewhere in the system

 

[DaRosa218]

Looks like I have an electrical issue, system won't read High Pressure Switch data. I am going to replace the wiring connector as it appeared to be corroded and will work my back to the BCM and HVAC controller.