Porsche Cayenne 92A Hybrid brake vacuum issue

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:

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

Case study: Mercedes-Benz C-Class, electrical fault

Opus IVS supports a workshop with an electrical fault malfunction on a Mercedes-Benz W205 chassis.

Opus IVS OEM brand-specific Master Technicians support its customers globally via its IVS 360 diagnostic support service, assisting workshops and technicians in the repair of complex vehicle technology.

Using the DrivePro’s diagnostic software and extensive product knowledge, the IVS 360 team provide workshops with the confidence to repair the most complex vehicles with speed and efficiency.

All of the IVS 360 team of OEM-Trained Master Technicians have extensive main dealership workshop experience, which Opus IVS keep up to date through ongoing VM and OEM training. This allows the IVS 360 team to have knowledge of the latest models and systems, enabling them to support customers effectively from initial diagnosis through to final repair.

Mickey Syrota, Mercedes-Benz Master Technician at Opus IVS recently supported a customer with an electrical fault malfunction on a Mercedes-Benz W205.

Using Opus IVS diagnostic software and his extensive brand knowledge, Mickey was able to identify the cause and provide his customer with step-by-step guidance needed to repair the fault.

Vehicle: Mercedes-Benz (C- Class) W205 chassis Issue: Auxiliary battery malfunction warning message

displayed on instrument panel cluster Fault codes presented: b21dc01

The Cause:

A code read was performed and sent via the customers’ DrivePro device, which revealed the following fault: ‘b21dc01 buffer battery of the EIS malfunction, there is a general electrical fault’.

The most likely cause of an EIS fault code is that one of the power supplies to the EIS switch (Electronic Ignition Switch) is not present. Mickey suggested that the most likely possible cause of a general electrical fault would be a result of the internal c8 capacitor shorting out.

Mickey also explained that the W205 does not have a separate auto start/stop battery, instead it has a current limiter device on the positive terminal of the battery under the bonnet, and that this works in conjunction with the C8 Park Pawl capacitor. Therefore, the cause would most likely be because of no voltage to the ignition switch on the 30b circuit. The voltage converter would therefore need to be inspected and tested along with the C8 Park Pawl capacitor.

The Fix:

The following steps were provided to the customer:

The C8 Park Pawl capacitor is in the N/S/F foot well area. Checks required:

1. At the C8 capacitor pin 2 = red 12v
2. Pin 1 = earth brown
3. Pin 3 = red/blue to EIS switch plug 1 pin 28, 30b voltage

To remove the C8 Park Pawl capacitor, the following guidance was provided:

1. Remove the N/S/F kick panel trim
2. Remove the glove box under dash panel
3. Remove the N/S/F section of carpet
4. Remove the plastic panel on the floor against the bulk head

The C8 Park Pawl capacitor is bolted to the left-hand side of the electrics panel, remove the 8mm nut and lift out the voltage converter. This feeds in to the EIS at plug 1, pin 28 =30b voltage.

The voltage supply to the C8 Park Pawl capacitor comes from the rear SAM control unit in the trunk/ boot from fuse 448.

Further remedies supplied:

Mickey further explained that if the C8 capacitor has shorted internally then it is possible that the feed into the EIS at plug, pin 28=30b voltage or additional battery voltage will still be missing after the repair, and still result in the same fault message on the dashboard.

If the voltage converter is replaced, and the fault remains, the following checks would be required:

1. K40/5 f448 (Electrical fuse 448)
rear SAM (signal acquisition module)
2. Check electrical lines, connections and connectors for damage, correct connection, loose contact and corrosion, and repair or replace if necessary
3. Check regulator and alternator
4. Additional battery
5. Replace C8 (Park Pawl capacitor).

For information on IVS 360 support, visit www.opusivs.com, email sales-uk@opusivs.com or call 01865 870 060.