Having access to the biggest USA workshop live hotline databases, I will publish them here and might help some.

Customer Concern: Door locks are inoperative with remote and inside switch. Trunk may not open as well.
Average Reported Mileage: 74347

Tests/Procedures:

1. Locate rear fuse panel and remove fuse #71. Reinstall with known good fuse. This should reset fault memory of Pneumatic System Equipment (PSE) and resume operation of door locks if there was a leak in the system. If fuse is blown, suspect failed Pneumatic System Equipment (PSE).

2. Locate Pneumatic System Equipment (PSE) pump in left rear of trunk. Remove all connections and inspect for corrosion on connectors. Replace when corrosion is found.

3. Using a fully functional Mercedes-Benz compatible scan tool, read/record/clear DTCs in the Pneumatic System Equipment (PSE) control module.

4. Using a hand-held vacuum tester or smoke machine, disconnect the individual vacuum hoses at the PSE pump in the left front of the trunk compartment and test at each line disconnected from the pump for leakage at each door and trunk actuator. If it leaks, either the vacuum/pressure line or the actuator in the door/trunk must be replaced.

5. If no leaks are found and the pump runs during lock operation without producing pressure or vacuum, then the Pneumatic System Equipment (PSE) is faulty. Tech Tips: A factory type scan tool will be needed to perform correct testing of this system along with replacement coding of the Pneumatic System Equipment (PSE). Do not recheck for faults by closing doors over and over and over. The pump will simply time out and set DTC and quit again. The Pneumatic System Equipment (PSE) uses vacuum to unlock the doors and to open the trunk. The Pneumatic System Equipment (PSE) uses pressure for closing assist on the doors and trunk. Pressure is also used to lock the doors. B1021- CONTROL MOD. A37 "PSE AND PNEUMATIC CONTROL MOD" NOT SENDING DATA ON CAN BUS.

Diagnostic Codes
B1021

Potential Causes
Leaking Door Lock Actuator(s)
Pneumatic System Equipment (PSE) Pump/Module A37
Leaking Vacuum Line

Confirmed Fix Summary

Confirmed Fix

18 - Replaced/Cleaned Pneumatic System Equipment (PSE) Pump/Module A37
8 - Replaced Fuse #71
2 - Replaced/Reset Door Lock Actuator(s)
1 - Repaired Vacuum Hose/Line(s)
1 - Replaced Trunk Lock Actuator
1 - Replaced Door Lock Actuator(s) and Replaced Pneumatic System Equipment (PSE) Pump/Module A37
1 - Replaced Fuse #71 and Replaced Pneumatic System Equipment (PSE) Pump/Module A37

Confirmed Fix Details

Tech Reported Fix Details Confirmed Fix

November 8, 2017 2009 Mercedes-Benz SL550, 5.5L, V8, USA
Pneumatic System Equipment (PSE) Pump/Module A37 Replaced Pneumatic System Equipment (PSE) Pump/Module A37

September 11, 2017 2009 Mercedes-Benz SL550, 5.5L, V8, USA
Pneumatic System Equipment (PSE) Pump/Module A37
31,600 miles Replaced Pneumatic System Equipment (PSE) Pump/Module A37

April 18, 2016 2004 Mercedes-Benz SL500, 5.0L, V8, MFI, USA *
Pneumatic System Equipment (PSE) Pump/Module A37
- (PSE) Pump/Module: pump failed.
Replaced Pneumatic System Equipment (PSE) Pump/Module A37

April 29, 2020 2004 Mercedes-Benz SL55 AMG, 5.5L, V8, USA *
Pneumatic System Equipment (PSE) Pump/Module A37
20,763 miles Replaced Pneumatic System Equipment (PSE) Pump/Module A37

April 29, 2020 2003 Mercedes-Benz SL500, 5.0L, V8, MFI, USA *
Pneumatic System Equipment (PSE) Pump/Module A37
111,000 miles Cleaned Pneumatic System Equipment (PSE) Pump/Module A37

April 29, 2020 2003 Mercedes-Benz SL500, 5.0L, V8, MFI, USA *
Pneumatic System Equipment (PSE) Pump/Module A37
63,000 miles Replaced Pneumatic System Equipment (PSE) Pump/Module A37

April 29, 2020 2002 Mercedes-Benz SL500, 5.0L, V8, Des 113.961, USA *
Pneumatic System Equipment (PSE) Pump/Module A37
136,000 miles Replaced Pneumatic System Equipment (PSE) Pump/Module A37

April 28, 2020 2005 Mercedes-Benz SL500, 5.0L, V8, MFI, USA *
Pneumatic System Equipment (PSE) Pump/Module A37 Replaced Pneumatic System Equipment (PSE) Pump/Module A37

April 16, 2020 2006 Mercedes-Benz SL500, 5.0L, V8, Des 113.963, USA *
Pneumatic System Equipment (PSE) Pump/Module A37 Replaced Pneumatic System Equipment (PSE) Pump/Module A37

February 12, 2020 2003 Mercedes-Benz SL500, 5.0L, V8, MFI, USA *
Pneumatic System Equipment (PSE) Pump/Module A37 Replaced Pneumatic System Equipment (PSE) Pump/Module A37

March 11, 2019 2006 Mercedes-Benz SL500, 5.0L, V8, Des 113.963, USA *
Fuse #71
- Found pump submerged in trunk. Repaired seal at base of rear window and dryed pump. Replaced blown fuse for pump. Found trunk was locked. Used mechanical key to turn trunk lock to correct position.
Replaced Fuse #71

March 22, 2016 2008 Mercedes-Benz SL550, 5.5L, V8, USA *
Fuse #71
- Module pulls a lot of current when locks are operated, not sure why.
Replaced Fuse #71

February 7, 2020 2007 Mercedes-Benz SL550, 5.5L, V8, USA *
Fuse #71
- in rear fuse box underneath rear seat
Replaced Fuse #71

June 1, 2016 2007 Mercedes-Benz SL550, 5.5L, V8, USA *
Fuse #71
- replaced fuse 71
Replaced Fuse #71

September 24, 2019 2005 Mercedes-Benz SL500, 5.0L, V8, MFI, USA *
Fuse #71
- water intrusion
Replaced Fuse #71

June 10, 2019 2011 Mercedes-Benz SL550, 5.5L, V8, USA *
Fuse #71 Replaced Fuse #71

May 4, 2018 2003 Mercedes-Benz SL500, 5.0L, V8, MFI, USA *
Fuse #71 Replaced Fuse #71

February 23, 2016 2007 Mercedes-Benz SL550, 5.5L, V8, USA *
Fuse #71 Replaced Fuse #71

July 10, 2019 2003 Mercedes-Benz SL500, 5.0L, V8, MFI, USA *
Door Lock Actuator(s)
- Both door latches were replaced and the pneumatic seats were plugged off with the gas door lock. Basically almost everything was leaking except the trunk.
Replaced Door Lock Actuator(s)

April 16, 2015 2005 Mercedes-Benz G55 AMG, 5.5L, V8, USA *
Door Lock Actuator(s) Reset Door Lock Actuator(s)

April 29, 2020 2004 Mercedes-Benz SL55 AMG, 5.5L, V8, USA *
Door Lock Actuator(s)
Pneumatic System Equipment (PSE) Pump/Module A37
101,000 miles Replaced Door Lock Actuator(s) and Replaced Pneumatic System Equipment (PSE) Pump/Module A37

April 29, 2020 2007 Mercedes-Benz SL550, 5.5L, V8, USA *
Fuse #71
Pneumatic System Equipment (PSE) Pump/Module A37
36,000 miles Replaced Fuse #71 and Replaced Pneumatic System Equipment (PSE) Pump/Module A37

September 25, 2019 2005 Mercedes-Benz SL500, 5.0L, V8, MFI, USA *
Trunk Lock Actuator
- Vacuum element was leaking

66,000 miles Replaced Trunk Lock Actuator

April 29, 2020 2003 Mercedes-Benz SL500, 5.0L, V8, MFI, USA *
Vacuum Hose/Line(s)
- Repaired air line under passenger seat for lumbar support.

77,000 miles

Vehicle Application:
2003 SL500 5.0
2004 SL500 5.0
2005 SL500 5.0
2006 SL500 5.0
2003 SL55 AMG 5.5
2004 SL55 AMG 5.5
2005 SL55 AMG 5.5
2006 SL55 AMG 5.5
2007 SL55 AMG 5.5
2008 SL55 AMG 5.5
2007 SL550 5.5
2008 SL550 5.5
2009 SL550 5.5
2004 SL600 5.5
2005 SL600 5.5
2006 SL600 5.5
2007 SL600 5.5
2008 SL600 5.5
2009 SL600 5.5
2009 SL63 AMG 6.3
2005 SL65 AMG 6.0
2006 SL65 AMG 6.0
2007 SL65 AMG 6.0
2008 SL65 AMG 6.0
2009 SL65 AMG 6.0

 

I would add to this for the benefit of others and also from personal experience, that if the PSE pump itself is not working there’s a good chance it’s repairable rather than just replace it (which is of course what the Manufacturer would advise for obvious commercial reasons).

Broken impeller is a common PSE Pump fault and in my case after a bit of reading and YouTube research I had the pump out of the car, repaired with a new impeller from eBay and back on the car inside 2 hours and £80 Sterling for the impeller. Having done it once I reckon I could do it again from start to finish, inside an hour.

 

Thank you for this positive contribution

 

Three important points:

1. For a MY2009 or newer car the correct fuse to pull for the PSE controller is #54; #71 is for COMAND.
2. A Keyless Go car does not use the PSE system for locking/unlocking, since it would be to slow. Therefore, the diagnostic procedure in the first post does not apply to Keyless Go.
3. A Mercedes-compatible scanner is not required to reset stored PSE codes. Removing the correct fuse powering the PSE accomplishes this.

 

You see, by posting it a kind way there is nothing wrong correcting these cases, thank you

 

Thats a surprise to me, always good to hear stuff I didn’t know, how does a Keyless Go System power unlock/lock?

 

The fact if these correction to the archive are accurate or not is the responsibility of the persons who make them. hope other people here can verify and confirm or not
I am too busy have fun

 

I’m just surprised because I have Keyless Go and my Central Locking very definitely works off the PSE pump. 2005 350

 

These were poorly-chosen words, Mat:The locking system in a KG car is nearly identical to a standard car. The difference is in the doors (the subject of this thread.) If the PSE pump were used to unlock a door that had its handle pulled, the lock wouldn't release the door in time. Consequently, you'd pull on the door, meet resistance, and a second or so later the door could open. Mercedes needed something quicker, so the doors on a KG car have a solenoid on the locks.

 

So when my PSE pump failed my Keyless Go Stopped working too (on the doors). Additionally I very much do get the delay you describe when I use it. I grab the handle and have to wait for a very brief period for the door to unlock before I pull the handle.

OK I’m editing to apologise. My perceptions were based from a time when I was dealing with low Consumer Battery voltages. I’ve just retried now and currently the car has no voltage issues. The Keyless Go is quick and I can hear an electrical click in the door.

Im sorry if I’ve come across argumentative, my perceptions were based around a different problem I had, once again many apologies