DPFE/Code 337 Problem


MA Ranger

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My check engine light (CEL) is on continuously in my '94 Ranger 3.0L. I conducted a KOEO test with a scanner and it showed code 337 (EGR Valve Pressure Transducer/Position Sensor circuit above maximum voltage). I replaced the DPFE sensor with an aftermarket "metallic" one I bought at a parts store (the old one that was on the truck was the same kind), but the CEL is still on and the KOEO scan still shows code 337.

I tested the DPFE sensors (both new and old) and connector with a multi-meter and got the following results:

Back-probe brown/light green wire (top of connector):

4.95 volts old sensor/4.98 volts new when connected to the DPFE sensor

0.07 volts when disconnected

Tested grey/red wire (middle of connector) for ground (with test lamp): good

Tested brown/white wire (bottom of connector) when disconnected to the DPFE sensor: 5.0 volts

I tested the EGR valve with a vacuum pump and it tested normal (engine stalled when gage on the pump showed 15 - 17)

Other than the CEL on all the time, the engine runs normal - not overheating, idle is o.k. and it runs normal under all operating conditions (no change in performance before and after the CEL coming on). The only time the CEL turned off was when I was driving home from work today - it went off for about 10 seconds after I hit a bump in the road. Other than that, it's been on for about a month now.

I suspect that the new DPFE sensor might be bad too, but I'm not sure and it seems odd that it would be bad right out of the box. Any help would be greatly appreciated.
 
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ranger98v

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do you have a factory service manual for that year/make /model? I might try checking voltage from the begining, meaning, start at the PCM. Then match your findings against the proper spec's. check all connections from the PCM out to the DPFE sensor and the any related parts, i.e; EGR solenoid, ...remember that a "code" isn't an exact science, it will only lead you in the right direction. Or in this case, to the right system(EGR). Check all connector's and wires for that system, with engine running give all lines and conecters a "wiggle" test. Have a partner keep an eye on the CEL while you do that. it may help you pinpiont the problem....that's were I would start.
 
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bean

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it has been my experience that aftermarket emissions related parts are not of the same quality as the originals. you may be able to obtain a motorcraft/ford at an autoparts wholesale warehouse. the cost is cheaper than from the dealer.
 

MA Ranger

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Thanks for the advice. The CEL doesn't come on right away now - only after you drive the truck a mile or two and it still goes off for about 10 - 30 seconds after you hit a bump "just right". I'm going to do some more diagnostic work this weekend.
 

Beef52751

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if it shuts off when you hit a bump it sounds to me like a loose connection.
 

MA Ranger

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The CEL still doesn't come on right away, only after the truck is driven a mile or two. It does this every time you start it regardless how much it was driven before you turned it off and whether the engine is hot or cold. However; the code 337 is gone - it's been replaced by code 332 (Insufficient EGR flow detected) during the KOEO test, both hard and continuous codes.

Test results for the DPFE circuit have also changed:

Backprobe brown/light green wire at the DPFE sensor connector =

a. 0.69 volts when connected
b. 0.10 volts disconnected

grey/red wire still shows good ground with test lamp

brown/white wire shows 5.02 volts disconnected
 
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MA Ranger

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I replaced the aftermarket, cast-aluminum DPFE sensor with an OEM plastic one I bought from Tousley Ford Parts Depot. This solved the CEL and cleared all codes I was getting with a code scanner. It's been a month now and no CEL!
 

Lonewolf

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thanks for the follow up.
So evidently these aftermarket sensors are a gamble.
 

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At least the DPFE sensors are. Apparently the problem is that they're cast aluminum and there's some "empty space" on the inside of their housing where the sensitive electronics are. This allows water to condense in the space over time and cause problems with the electronics. The sensor a bought from Tousley Ford Parts Depot is a plastic, solid part - no space or "cold metal parts" to icrease the risk of water condensation. The sensor was a generic, "one size fits all" that required splicing three wires. But the instructions were good the design of the plug and sensor were better than the originaly installed OEM parts and it was about the same price as the aftermarket sensors sold at the parts stores.

I have bought other sensors and electronic parts from parts stores (e.g. a throtle position sensor, fuel pum relay and EEC system relay) and had good luck. So, it depends on the sensor.
 


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