Piston Slap: No OBD-II Code, No Clue Edition

by Sajeev Mehta

Published: December 11th, 2009

piston slap no obd ii code no clue edition

TTAC Commentator Detroit-Iron writes:

I have a 2000 Ford Ranger, 2wd 3.0L V6 with 143k miles. The CEL has been on for at least last 70k and I finally went to AutoZone and got the code read. Turns out the O2 sensor is bad and the EGR valve is stuck. Is that the kind of thing that I can fix myself? I don’t want to put a whole lot of money in this truck seeing as it has a lot of miles and has been running reasonably well, if inefficiently (21 mpg all highway), for so long. I have an ok tool set and I do my brakes, but I recently paid $70 to have the fuel filter replaced-I’ve done it before and I didn’t want to do it again. The truck is going back to my parents to be semi-retired and put into “farm use” so I wouldn’t mind fixing it up a little before giving it back but I don’t want to spend a lot.

Sajeev Replies:

No soup for you until you get the actual code from AutoZone! Never, ever throw parts at something: always ask the engine computer what’s wrong, then Google the code for a diagnosis.

Days later, Detroit-Iron replies:

Finally got the code again. It is P1400, it looks like a couple different possibilities ranging from a bad hose to a short. The funny thing is, the first time I got them read (and promptly lost the slips) am pretty sure there were two codes, the other being for a misfire. The print out is as follows:

Definition: BBDPFE ciruit low voltage detected.

Explanation: BBECM detected the EGR pressure sensor (DPFE) voltage below expected values

Probable cause:

BB1.-Failed DPFE sesor (EGR pressure sensor)

BB2.-Open or short circuit condition

BB3.-Sensor hose defective

Sajeev answers:

See, isn’t that much better? Back to your original question: yes, you can fix this yourself. And after your second email, you know where to attack the problem. Let’s not worry about the misfire you may have for now, because the EGR system is your biggest problem.

I had the similar code with my Lincoln Mark VIII, a new DPFE sensor (LINK: http://www.focushacks.com/?modid=80&ht=DPFE%20Sensor%20and%20EGR%20Information) ) fixed the code, it’s usually the fail point on this diagnostic tree. Before you pull the trigger on a new sensor, check the rubber hoses going to/from the DPFE before you buy a new sensor, maybe the vacuum line (BB3, from above) is cracked or rotted. And do a visual on your EGR wiring to make sure that BB2 isn’t the problem.

Bonus! A Piston Slap Nugget of Wisdom:

Don’t cheap out on replacement engine control sensors. Stick with OEM or a name brand like BOSCH or Borg-Warner to ensure you don’t replace this part 12 months from now.

(Send your queries to mehta@ttac.com)

#Engine #Ford #OBD-II #PistonSlap #Ranger #TroubleCode

Sajeev Mehta

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4 of 20 comments

Andy D on Dec 12, 2009

Generic advice. To de- pressurize a fuel system for service. Start the engine, remove the fuel pump fuse. When engine stalls, turn off key. Always, just " crack" a pressurized fitting to let it bleed.

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- Sajeev Mehta on Dec 12, 2009
  
  Sometimes pulling the fuse doesn't do a damn thing. Learned that the hard way with a Mondeo-Cougar, and I couldn't find the fuel pump shut off switch either. The best way is to let the car sit overnight and crack it open before you put the key in the ignition. Fuel systems (maybe not on direct injection systems) lose all their pressure overnight, hence the reason for the fuel pump whine you sometimes hear when you turn the key on. Wear rubber gloves before you get under the car and you may not get any gas on your skin too. Easy.
  
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- Rocketrodeo on Dec 12, 2009
  
  Specific advice: there's a fuel pump switch above the passenger side kick panel. No fuse pulling required. I've never even had a drip replacing the fuel filter. Unfortunately, it's an expensive filter. The replacement part is an aluminum canister clipped into a steel bracket that bolts to the frame as an assembly, and replaces the original one-piece rotomolded plastic filter. I have yet to find a p/n for just the canister. 2000 model Ranger w/ Vulcan and 5-speed, 130K and the most trouble free vehicle I have ever owned, including three hondas, two acuras, two toyotas, and two nissans; there is something to be said for decade-plus production runs. As the OBD port is currently occupied by a ScangaugeII, I'll know pretty instantaneously what a CEL indicates, should the truck ever throw one. It hasn't yet.
  
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RogerB34 on Dec 12, 2009

Change out the two upstream O2 sensors. Bosch for about $50 each Standard for $42 each. EGR valve is about $40. Way past their lifetime. Check for access, use a little penetrant on just warm exhaust. O2 socket will cost about $10.

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