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Autologic Case Study – Volvo V50 – intermittent loss of power

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A workshop was presented with a Volvo V50, which had a 4-cylinder engine, that lost power intermittently when driving. The car had been to the owner’s local garage and they had fitted a throttle pedal based on the fault code. After fitting the new part, the problem was not fixed and as a result, the car was returned a week later.

The car was now with an Opus IVS customer and they requested help in trying to solve the problem, as they were unfamiliar with this particular Volvo model. A quick test was sent in from the Opus IVS DrivePro diagnostic device, displaying ‘ECM (Engine Control Module) fault code 9520 Accelerator position sensor, signal too low/high’. This is a common misdiagnosis that leads to a replacement throttle being fitted when it is, in fact, a wiring issue.

The pedal sensor has two signals – one direct to the ECM (PWM, Pulse With Modulation, signal) and the other is analogue to the CEM (Central Electronic Module), which is then conveyed to the ECM over the CAN network for pedal-check correlation.

The Autologic Master technician advised the customer involved wiring and pin grip checks from the pedal to the ECM and CEM:

PEDAL PIN CHECKS

1. 5 Volt supply from CEM plug G pin 22

2. Analogue output signal to CEM plug G pin 31 (0.15 volts pedal released; 4.85 volts pedal fully pressed)

3. 4-cylinder engines, sensor ground to CEM plug G pin 7.

4. Ground to chassis

5. Output to ECM (PWM) approx. 6% pedal released, approx. 90% pedal fully pressed (plug and pin designation, ECM variant dependent)

6. Fused battery volts supply (engine bay fuse board).

As a result of the above diagnosis from the Opus IVS Master Technician, the car was successfully fixed, leading to one happy garage and ultimately, a happy customer.

TECHNICAL TRAINING VIDEOS

Various technical training videos can be found on the Opus IVS website, covering marque-specific service functions, as well as training videos, including VW/Audi VVT testing and diagnosing, coding and programming, BMW ISTA Pass-Thru and VW Audi ODIS. Click HERE to view.

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