Some 2007 Mazda B-Series vehicles may experience MIL illumination with DTC P0401 in memory. This symptom may be caused by a damaged EGR vacuum tube inside the vacuum harness because the vacuum harness is misrouted.
- Retrieve the DTC and if code P0401 is the only code present, continue to Step 2. If P0401 is not present, do not continue with this bulletin, or if other DTCs are present, resolve those first before continuing with this bulletin.
- Inspect the EGR vacuum harness to ensure proper vacuum harness routing.
- If the vacuum harness is routed properly, perform normal diagnostics according to the workshop manual. If the harness is routed incorrectly, disconnect at the manifold and inspect for damage.
- Reroute the vacuum harness above the EGR valve. If needed, replace the harness. A replacement vacuum tube is available under P/N 1FAB-13-942.
- Clear the DTC and verify the repair.
The vacuum harness should run above the EGR valve as shown here.