error code p0420, and p0452. What are the possible causes? Are they related to one another? Is there an inexpensive solution?

15

Asked by Jan 04, 2016 at 08:51 PM about the 2006 Ford Freestar SE

Question type: Maintenance & Repair

The car hesitates at initial acceleration. Power flattens out when driving on
freeway. Need to pass smog real soon. I had a minor tune up recently and van
ran better for a short period. Check engine light came back on.

5 Answers

62,815

They're not related. P0420 is a catalytic converter code (below minimum efficiency threshold) and the P0452 is for the pressure sensor in the gas tank. It's reading unusually low pressure in the tank. Could be the sensor, the wiring going to the sensor, or a faulty component in the EVAP system. Perhaps even the gas cap. HTH. -Jim

1 out of 1 people think this is helpful.
6,315

They can be related in one specific set of circumstances. If the truck also wants to idle low or die at stops you probably have the vapor management valve under the hood sticking open. It will allow excess vacumn from the engine to pull on the gas tank and suck fuel vapors at the wrong time. If its stuck open it the extra fuel in the vapors can cause loss of initial throttle and stalls at stops along with reduction of catalyst efficiency. It's pretty easy to check, if it's off the vehicle and you can blow through it then its bad as it's a normally close valve. The Ford base part number for it is 9C915

3 out of 3 people think this is helpful.
15

Thanks Guy, Thats helpful. Nobody has mentioned a Vapor management Valve yet. Where under the hood might I find it? The stuck open sounds like a possibility. This may be the cause of the catalyst code... ?

1 out of 1 people think this is helpful.
62,815

This won't cause the catalytic converter code. The catalytic converter is monitored by the downstream oxygen sensor. If the computer sees too much variation in the downstream oxygen sensor that indicates that the catalytic converter is no longer working properly. How the computer tests the catalytic converter is the air/fuel mixture is momentarily made rich (more gas). If the catalytic converter doesn't "eat" the excess emissions there will be a jump in the signal from the downstream oxygen sensor. My guess here is that the EVAP system problem has been going on for awhile and damaged the catalytic converter similarly to the engine misfiring and dumping raw fuel into the catalytic converter. I'd fix the EVAP problem first then replace the catalytic converter. Otherwise you may damage the new converter. HTH. -Jim

6,315

It should be tucked under the cowling passenger side engine compartment.

2 out of 2 people think this is helpful.

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