1-4 CEL resolution... YEAH!!

My TS has been nagged by an intermittent problem where bank 1-4 would stop running after the car had been turned off for 10-15 mins post full warm up. I would get the CEL if I drove it and cancelling CEL errors etc.. would not always bring it back to running properly. Sometimes it would "fix" itself overnight, very difficult to isolate the problem. I tried everything, switching the MAF, the O2, ECUs, Cat ECU... finally cracked the code this week end.

I decided to check spark (old fashion troubleshooting instead of relying on ECU) and crack a fuel line to see if the pressure was ok, plenty of spark but no fuel. Checked fuses and relay, fuses ok, relay clicked. Checked Fuel pump voltage - 0 volts... ECU is obviously sending signal because relay is clicking... remove relay and replace with Aux Fan relay (no spare). Bank 1-4 is alive and runs fine!

Bottom line is that the fuel pump relay is at fault, is works OK but must be getting old (using it now on the Aux Fan) and must have enough internal resistance/corrosion that it does not always close the circuit. I think, this causes a cascading effect with the O2 and MAF trying to compensate... and resulting in CELs.

I guess the old way is still the right way.. is there spark and fuel? then work your way to the ECU errors codes

Franck