I own a 1997 Dodge Caravan 3.3 liter V/6. The check-engine light came on and the code was P0401 low EGR flow. The mechanic replaced all the parts in the EGR system and said the system is working as designed. He said the computer may have to be reprogrammed. What are your thoughts?

Question: I own a 1997 Dodge Caravan 3.3 liter V/6. The check-engine light came on and the code was P0401 low EGR flow. The mechanic replaced all the parts in the EGR system and said the system is working as designed. He said the computer may have to be reprogrammed. What are your thoughts?


Answer: I see this problem on vehicles often. Just because there is a fault code for a particular system does not necessarily mean the problem is in that circuit or system. On your particular case the problem could be a slow (lazy) front oxygen sensor. A normal operating oxygen sensor voltage will change as soon as the EGR opens and closes. A lazy front oxygen sensor is operating fast enough not to set an oxygen sensor code, but not fast enough to see the EGR valve is opening and closing as it should. Both you and I can give thanks to Identifix for this fix and many others.


 


Question: I own a 1997 V/6 Camry. My problem is when the temperature goes below 30 degrees the brake pedal is hard to push down until the engine runs 30-45 minutes. I have had the car to a couple of shops and neither can find the problem. Do you have any ideas?


Answer: There is no question that water is collecting and freezing up. The most common problem I have found is a leaking power brake booster. A leaking vacuum brake booster will actually suck runoff water in a rainstorm and will freeze in below-freezing temperatures. A leaking brake booster can also be a cause of lean engine fault codes. An easy way to check to verify the booster is leaking is pour water around the booster and listen for any sound change. The second way is start the engine, shut the engine off, press the brake pedal and see if the brake pedal is hard to push the first and second time. A normal brake booster will vacuum and enable the brake pedal to be easy to push one or two times. If the pedal is hard the first push, you need to check both the brake booster and rubber vacuum seal. Price check around for a remanufactured brake booster. There is a big difference between rebuilt and new.


 


Question: I own a 2007 BMW 3 series. The check engine came on and the shop scanned the computer and found an evap p0456 small leak. The shop spent a lot of time using a smoke machine. Two of the technicians worked on the car for three hours and could not find the source of the small leak even though the smoke machine confirms there is a small leak and have narrowed it down to the gas tank. Without seeing any smoke they do not know what more to do. The shop is out of ideas, do you have any?


Answer: We see a lot of evap leaks. Some we can find with the use of both a scan tool and smoke machine and others not so easy to find. A smoke machine blows smoke at about one pound. We have found using a soap and water solution all over all the sealing gaskets and plastic lines can usually help find the leak.


Junior Damato writes regularly about cars. You can send questions to him care of the Old Colony Memorial, 182 Standish Ave., Plymouth, MA 02360.