XJ40 ( XJ81 ) 1986 - 1994

Fuel Fail 37

 
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Old 08-28-2018, 10:42 AM
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Default Fuel Fail 37

Over the last couple of weeks the check engine light came on a couple of times - something that hasn't happened in quite a few years.

Assuming it was just a bad connection, I re-plugged all the common engine sensors. cleared the code but forgot to actually check the VCM ...of course, once the light was reset it was too late to read the code because I'd cleared it with the battery disconnect.

Not to worry though, it came back about a week later and I was surprised to see an FF37 flagged - a new one on me. After a quick google I found FF37 is an electrical fault related to the blue EGR solenoid above and at the rear of the engine.

General consensus on the net was that the failure can often be a dirty connection at the sensor and that a clean and re-plug of the connector was sometimes all that was necessary - so that's exactly what I did - however, yesterday the CEL came on once again, flagging the same FF37 code.

I was out at the local lake when the code flagged so I thought I'd head over to my parts stash and have a look for a replacement solenoid, but first thought it was worth checking the little box of "Jag goodies" in the trunk ..and ...at the bottom of the box, there they were, three replacement blue Denso EAC 7905's!
Not sure why I had three, but there they were!

Anyway, one bolt and two vacuum hoses later, fitted a "new" one, cleared the code and drove home. When I refitted the vacuum hoses they felt a bit tired and slack, so today I'm going to trim them back a bit and refit. It'll also give me a chance to make sure nothing is blocked. Apparently the vacuum hoses can plug up, also causing the ECM to set the FF37.

Hopefully I've cured the problem - now it's just wait and see...!

Larry
 

Last edited by Lawrence; 08-28-2018 at 10:46 AM.
  #2  
Old 08-28-2018, 01:17 PM
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Back in the mid to late 1990s I had a 4.0 XJ40 that would NOT clear a FF37 DTC no matter what I did.
I replaced the vacuum solenoid valve with known-good and even installed it on a different car.
Checked the wiring (OK).

I finally swapped ECMs with another car and the fault followed the ECM.

I guess the output semiconductor in the ECM for the solenoid failed??

bob
 
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Old 08-28-2018, 02:12 PM
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Oh Joy!

Lets hope I got it (however I do have a spare ECM if it comes to that)

Larry
 
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Old 08-29-2018, 12:55 AM
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Tested the old unit on the bench today and it read 43.9 ohms which I think is within range?

Larry
 
 
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