[xj-s] Check engine code FF39

XJ-S
1

My check engine light came on last night, as I was driving
home from my weekly poker game (not that that has anything
to do with the engine, but I thought that I would just
mention it in passing)The car is a 1994 XJS 4.0 litre 6
cylinder converible The computer shows a code of FF39 and I
can find no mention of this code in any of the books that I
have. Does anyone out there have any information on this
code, it is definatly FF39, I disconnected the battery for
about 10 minutes this morning, reconnected it and even
after warming up the engine there was no check engine light
so I am hoping for the best, but I would still like to know
what this code means as I am sure that it will return. I
appreciate any help that you can give me on this.

Thanks and have a great Jag day…Terry Spoor–
1994XJSCONVERTIBLE
MARLBORO N.Y., United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

// please trim quoted text to context only

2

In reply to a message from MR.S sent Sun 16 Oct 2011:

FF39 is for the EGR temp sensor circuit.

You need to download Jaguar Publication S-91 AJ6 4.0Liter
Engine Management OBD Diagnostic Guide.

It explains the engine management and has guided diagnostics.

Do a web search or find an older Jag mechanic that went to
the training seminars back in the early 1990’s and still has
the booklet.

You probably have a clogged EGR port at the intake manifold
(common) or failed EGR valve.

bob gauff–
The original message included these comments:

mention it in passing)The car is a 1994 XJS 4.0 litre 6
cylinder converible The computer shows a code of FF39 and I

–
Bob Gauff Owning and Repairing Jaguars Since the Early 70’s
Decatur, TX., United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

// please trim quoted text to context only

3

In reply to a message from motorcarman sent Sun 16 Oct 2011:

The ff39 code is for the egr temperature sensor. It still may be
the egr valve that is the problem. I had to replace my egr valve.

Tom 95XJS 4.0L coupe–
The original message included these comments:

FF39 is for the EGR temp sensor circuit.

–
tomjag95
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

// please trim quoted text to context only

4

My trip computer check engine is showing FF39 on my 94 xjs 6cyl.Can
anyone advise me whwt my promlem is? I just seem to have one
problem after another. I guess this is just part of the joy of
ownership of these fabulous cars. Thanks in advance, Ron–
94 XJS 4.0L conv., 03 S type-5 spd manual
Winston-Salem, NC, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

// please trim quoted text to context only

5

In reply to a message from RGW1220 sent Tue 2 Dec 2014:

EGR is a likely suspect. Does it appear original? The
diaphragm is probably shot. Hope this helps–
The original message included these comments:

My trip computer check engine is showing FF39 on my 94 xjs 6cyl.Can

–
Stringbean- 94 XJS 4.0L convert BRG
Oklahoma, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

// please trim quoted text to context only

6

Old thread, but possible help with those fighting the FF 39 code. The code is due to the EGR temp sensor not seeing the hotter air from the EGR valve and pipe being returned to the throttle body. On my 94 4l, after confirming the EGR valve, vacuum, and return were operating properly (and reading the pipe temperature), I measured the temp sensor and found it to be open (infinite resistance). The ONLY thing the EGR temp sensor does is to verify proper resistance (via the ECU returned voltage) that indicates that indeed the EGR system is functioning properly. The sensor is both expensive and difficult to access. Other forums for other vehicles have extensive write ups on putting a resistor in the connector to “fool” the computer into not flagging the ff39 code. Given the characteristics of the NTC sensor, I put a 68K ohm resistor into the connector going to the ECU (unplugged the sensor wire). The result was that I eliminated the ff39 code. Note that I did this AFTER verifying that all the EGR functions were performing correctly. I would rather not have this code mask other codes that activates the check engine light. This also would work for xj40 and probably earlier xjs/xj6.