Recently got an '06 v6 automatic Mustang, it is currently reading this error code. A month or so ago, I replaced the EGR valve, (which on the v6 mustang seems to include the DPFE sensor), which apparently resolved the p0401 & p0402 error code it had, at the time.
About a week ago, after almost a solid month of driving without any concerns, the p0405 popped on.
As someone with basic, mostly self taught mechanical experience, (brake change, starter engine replacement, minimal tools...) how likely is it that I could resolve this problem? From what little research I have done it seems a few diagnostic tools could be required, such as a vacuum gauge and a volt meter. As someone who does enjoy the DIY, should I own them? And as a final question, if I were to bring this to a mechanic, should I expect the repair to be affordable?
Thank you!
If you're planning on keeping your 2006 Mustang then you certainly should start building up a toolbox with things like a handheld vacuum pump and a multimeter (select a multimeter that can measure Hertz frequency).
If you don't have a scanner then you should buy the best one that you can afford. Take a look at @daywalker 's sticky at the top of the forum homepage, Which Scan Tool Should I Get?
In the case of a P0405 (or P0406) code, those are circuit voltage codes.
405 is low voltage and 406 is high voltage.
On yours they're specific to the DPFE input circuit.
The thing is, your EGR valve isn't controlled by vacuum. So a vacuum pump wouldn't be much help here and this isn't an EGR Flow DTC.
Yours is really an EGR module. It has all the EGR controls in one unit. (EGR control ((not by vacuum yours is a stepper motor)), DPFE sensor ((yours doesn't use an orifice in the EGR valve to the exhaust pipe manifold connection)), EGR valve itself).
It's a low voltage code. The voltage the computer is receiving is Out Of Range. All that means is that when the computer commands the EGR valve completely closed, it's seeing a DPFE voltage that is lower than what it should be seeing when the EGR valve is completely closed. For example. let's say when the EGR is completely closed the computer expects to see 0.2 volts from the DPFE sensor. Yours is lower than that.
Something in the circuit is probably shorting to Ground somewhere ((signal low voltage)) so check the connector at the EGR module and that harness connection just below it for corrosion and the wiring between the two for damage.
You can't rule out a faulty replacement part (shorting to ground internally) but that would largely depend on if you were able to get OEM or aftermarket.
a vacuum gauge and a volt meter. As someone who does enjoy the DIY, should I own them?
yes. Both are inexpensive and indispensable tools.
