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Porsche Cayenne 92A Hybrid brake vacuum issue

By autotech-nath on December 1, 2021

CASE STUDY: Opus IVS supports a customer with a Porsche Cayenne 92A Hybrid brake vacuum issue.

IVS 360, from Opus IVS, provides diagnostics and live repair guidance support services to help workshop technicians fix complex vehicles safely and fast. All Opus IVS mechanical repair solutions come with live repair guidance from IVS 360 OEM brand-specific master technicians.

Using the DrivePro’s diagnostic software and extensive product knowledge, the IVS 360 team identifies the cause and steps needed to fix vehicle faults. Support from the team can be requested directly from a DrivePro device or DrivePro Elite Diagnostic Kit.

Opus IVS’ experts remote in real time directly to vehicle communication systems to diagnose, program and calibrate vehicles. This eliminates the uncertainty, giving workshops the confidence to get the most complex vehicles back on the road safely and fast.

A recent case involved a Porsche Cayenne 92A 2011 model year. The vehicle had a hard brake pedal, which indicated a fault with the electrical vacuum when switching to Hybrid Drive. The IVS 360 team supported the customer with the following advice:

Make: Porsche

Model/Yr: Cayenne (2011 – 2017) Hybrid

Symptoms: Hard brake pedal

Example picture of Cayenne engine bay relay board.

The brake servo has a mechanical and electrical vacuum pump to create the required vacuum for the brake servo. When the vehicle switches to hybrid drive the electrical vacuum pump is used, or at a time the mechanical pump does not make required vacuum when the engine is running.

Fault codes: P147900 Brake boost vacuum system, mechanical failure DME – ENGINE ECU

The repair:

1. Connect your diagnostic tool and read out the fault codes

2. Checking the vacuum of the mechanical pump:

  • If P147900 is stored then check actual values of the mechanical vacuum in the DME data list.
  • The expected vacuum pull is approx. 550 down to 800 hpa (550 – 800 hpa/millibar, = 0.55 – 0.80 bar) vacuum.
  • The mechanical pump is located on the front of the engine Bank 2.

3. Check the vacuum pipes

The vacuum lines contain check valves, so be sure these are working. Check the vacuum lines for micro cracks. There are other vacuum systems for the control of the Secondary Air injection, intake manifold flaps. The solenoids (2 for Air injection, 1 for inlet manifold flaps) are mounted at the rear of the engine on a bracket. There is another vacuum line and solenoid for the engine coolant pump (water pump) shutoff slide control at the front of the engine.

4. The electric vacuum pump

The electrical pump is mounted lower on the engines side, near the front of Bank 1. The electrical pump is powered via a relay (3) in the under-bonnet fuse board, maxi fuse (4) provides the pump protection, the DME switches the relay depending on the pressure sensor reading. The pressure sensor is mounted in the vacuum line near to the brake servo.

5. Test the electrical vacuum pump

Check that the electrical vacuum pump runs and will create the required vacuum. Do this with engine off key on, the relay can be worked from the DME drive link function (or bridge relay) The DME only monitors the control of the relay not the pump electrical function.

6. Replace the electrical pump

If the electrical pump is determined to be faulty, i.e. not running (fuse and relay ok) noisy during operation, or is getting hot quickly, replace the electrical pump always together with the relay (3) and maxi fuse (4).

Tools required:

• Diagnostic tool

• Hand vacuum pump

• Smoke tester (optional)

For more information on Opus IVS diagnostic solutions and IVS 360, please visit www.opusivs-uk.com.

T: +44 (0) 1865 870 060 E: sales-uk@opusivs.com

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Autotechnician is a magazine published nine times a year, delivering essential information to independent garage owners and technicians in the UK. Delivered both digitally and in print, autotechnician provides readers with technical, training, business advice, product and news, allowing our readers to keep up to date with information they need to run and work within a modern workshop.
About Autotechnician
Autotechnician is a magazine published nine times a year, delivering essential information to independent garage owners and technicians in the UK. Delivered both digitally and in print, autotechnician provides readers with technical, training, business advice, product and news, allowing our readers to keep up to date with information they need to run and work within a modern workshop.
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