A common problem in 2007 and 2008 Jetta 2.5 engines involves a faulty wire in the “Motronic ECM Power Supply Relay” (J271) circuit. This issue can be diagnosed and repaired using a Vcds 2.5 1k0 907 379 P interface. The fault often lies within a red/black wire approximately 10 inches from the ECM, exhibiting a “green puff” or blister, not necessarily a simple rub spot.
This damage is suspected to originate from a manufacturing defect – a purposeful poke or puncture in the wire during harness assembly. Over time, this damaged area corrodes and expands, increasing resistance and creating a hot spot. This eventually leads to communication failure between the ECM and the relay.
Seam Ripper for Wiring Harness
A seam ripper can be used to carefully remove the wiring harness tape for inspection.
A simple ohm test might not reveal this issue. While the wire might show acceptable resistance (e.g., 0.3 ohms) under no-load conditions, the damaged section can’t handle the current required to activate the J271 relay, preventing the ECM from communicating. Using a VCDS 2.5 1K0 907 379 P can help pinpoint the problem more accurately by reading fault codes and monitoring live data.
When inspecting the wiring harness, carefully remove the tape using a tool like a seam ripper, ensuring no wires are accidentally cut. Once the damaged section is located, repair is necessary. It’s crucial to adhere to VW and Audi’s repair guidelines, which specify crimp repairs only – no soldering – on the wiring harness. Using the correct repair procedures ensures a reliable and long-lasting fix. A VCDS 2.5 1K0 907 379 P scan tool can then be used to clear any fault codes and confirm the successful repair. Addressing this issue promptly can prevent further complications and ensure the vehicle runs smoothly.
