A persistent “Manifold Pressure Sensor (G71) Open / Short to Ground” error (OBD2 code 17564) plagued my VW T4. This article documents my troubleshooting process, from replacing the Mass Air Flow (MAF) sensor and air filter to investigating the Manifold Absolute Pressure (MAP) sensor and vacuum hoses. If you’re experiencing similar issues with your VW T4 and an OBD2 scanner is reporting related codes, this might help.
Initial Steps: MAF Sensor and Air Filter Replacement
My initial suspicion fell on the MAF sensor. After replacing it with a remanufactured Bosch unit and installing a new air filter, the van initially showed improvement. The boost was noticeable around 2,500 RPM, but soon the sluggishness returned. Connecting my OBD2 scanner revealed the single error code: 17564.
Further Diagnosis: MAP Sensor Testing
Clearing the 17564 code and disconnecting the MAP sensor resulted in two codes: 17564 and 17569 (Manifold Temperature Sensor). Since these sensors are often integrated into a single unit, this wasn’t surprising. Reconnecting the MAP sensor and clearing the codes brought back the persistent 17564 error. Using VCDS (Vag-Com Diagnostic System) to monitor Measuring Block Group 10, both the atmospheric pressure and boost pressure readings were identical and remained static regardless of engine speed or status, confirming a faulty MAP sensor.
Next Steps: MAP Sensor Replacement and Vacuum Hose Inspection
A new MAP sensor is a relatively inexpensive fix. Replacing it seems like the logical next step before delving into the more complex task of inspecting the wiring loom for breaks. However, the poor condition of the vacuum hoses, with significant wear and tear on the outer braiding, also warrants attention. Replacing them with silicone hoses is a preventative measure I’ll be taking. Determining the correct hose gauge(s) for a VW T4 is crucial for this task.
Conclusion: Continuing the Troubleshooting Process
While replacing the MAF sensor and air filter didn’t resolve the issue, it narrowed the problem down to the MAP sensor and potentially the vacuum system. Replacing the MAP sensor and inspecting/replacing the vacuum hoses are the next steps in this ongoing diagnostic process. Using an OBD2 scanner along with diagnostic software like VCDS provides invaluable data when troubleshooting these types of problems on a VW T4. Hopefully, these steps will lead to a solution and restore the van’s performance.
