Hello.
I'm having issues with my Jaguar X300 3.2. The problem is that the oxygen sensors are not regulating properly. From what I’ve been able to measure and from reading various forums, it seems the ECU is the root of the issue. Additionally, when I read the fault codes on the car, I get the code P1777, which indicates a fault with the TCM module. However, since my car has the older automatic transmission that doesn't use a TCM, I suspect that the previous owner might have replaced the ECU at some point and installed the wrong one.

Now I’m stuck trying to figure out how to identify the correct ECU for my car. What exactly should I be looking for on the box to ensure I get the right one?

 

You probably don't need a module but simply the correct PROMS installed.

No idea what PROMS are required for 3.2 (or ROW) but the North American market had a RECALL for PROM replacement.

This is what is involved with PROM replacement.
Finding a 'good-used' is likely your option.

 

The 3.2 liter with the ZF4HP 22 does not have a transmission ECU , the ZF4HP 24 used on the larger 4.0 liter has the transmission ECU as a more expensive feature same basic transmission ( minus shift electrical controlled solenoids used instead of old school fluid controlled shift logic ) , cost

Matter of item name calling

The Transmission ECU is different than the TCM ( traction control module ) and TCM is located fwd of the brake anti skid module

The TCM was an optional throttle cable retracting item separate from the transmission type

As Bob mentioned the upgraded ECU should ( if the TSB instructions followed ) have a small R - 493 sticker on it

You may not even have a EGR valve located on the intake manifold on top

P1777 as label Adaptive Fuel Metering Trim Too Rich

Page 128

801S TITLE

 

I see a difference in P1777 between the years as the 1995 has a separate 1995 CEL code list

Yours first production 1994.5 ? with the hockey puck on the top right fwd on engine ? this is a cam position sensor instead of and in same place the earlier distributor cap with spark plug wires

P1777 on page 119 in this case

Still researching

What are your observations to point to the O2 sensors ?

There is 1 fuse for all O2 sensors heaters to be above a sensor temperature to read correctly

These heaters inside the O2 sensors can be bad and read easily with a common meter which ensures the O2 sensors read correctly

Fuse # 14 / 10 amp right engine bay fuse box , this is point 33 in the pic below for a 4 O2 sensor engine ( yours may be only 2 as the rear )


'
This is the red ECU connector for the O2 sensor feed and return ( feedbacks ) to the engine ECU signal wires , not including heaters

 

The engine ECU part #s can be found here

The 4.0 is different than the 3.2 internally ( software )

Genuine Electronic Control Module-3.2 Litre (3.2 Litre) For Jaguar Xj 1995 - 1997 (from 720125 To 812255) (x300) Classic | Jaguar Land Rover Classic Parts

Notice your country's ( Denmark ) specification but may have a Great Britain region first production " build "

Bottom line is if the car will pass current Denmark emissions sniffer test if required

There is a problem in simply only step replacing the engine ECU if done in the past ( suspected )

 

I will ask an obvious question.

Have you replaced the oxygen sensors?

Also, have you seen this?

http://jagrepair.com/images/TSB/TSB2/XJS_XJ40/44Auto%20Gearbox/44-29%20DTC%20P1777%20%E2%80%93%20Updated%20Module.pd f

The code p1777 is rather interesting because it is the code specifically mentioned in this TSB.

 

Link works above if removing the space in the last PDF lettering

To be

http://jagrepair.com/images/TSB/TSB2...d%20Module.pdf

This one does get back to 4.0 transmission ECU labeled TCM in this case , again name referencing

Again the 3.2 liter ZF24HP 22 transmission does not have a transmission ECU that I'm aware of

Located passenger foot well next to fwd wall as a long ribbon connector made by TRW or Bosch

 

Yes, I replaced both of them which didn't fix the issue, that's why I suspected the ECU was the problem. I have read the TSB, which made me buy a used TCM module only to find out that my car didn't have one...

 

Fuse # 14 / 10 amp right engine bay fuse box and connector clean of the O2 sensor connectors

The ground post as the 2 ( 1 left side , 1 right side ) smaller ones on the rear engine firewall below the 2 larger B + ones

These ground post protects the O2 sensors return signal in the mini coax sheilded wires

 

So just to summarize, it could be something as simple as a fuse? If you do a "readiness test" on the diagnostic tester, it says the oxygen heaters are not ready, but wouldn't they adapt even if the heater in the sensor went bad?

 

The physics of the sensor precludes no or bad readings below a certain temperature not warmed up

With a 1st generation and 1st engineering try of ECU technology I would not expect the ECU to behave like you would have designed it and a check list that it does . Engineers have a manpower and time deadline to get it out the door as they integrate the delivered ECU manufacture's package into their package of the engine

The heaters do turn off after a period of time so the question becomes what about a stop light letting them maybe cooling down or maybe during your test time window not having the heaters powered ?

There is also the validity of the reader device which is not perfect

The reader can be defaulting to the more common O2 sensor then how a Titania sensor behaves

But then the heaters have only 1 independent ground path wire each sensor to the ECU and can read current from that before it gets grounded

The Lambda calculating return wire and it's interpretation is another matter as the final signal output to the ECU in expected range ?

 

I had this happen to me one time. My oxygen sensors worked, the heaters worked...it just flat lined though. No flip flopping, or anything.

It was indeed the ECU that was the culprit. I think it wasn't relaying info back to the sensors. They should always be chasing a perfect ratio....but mine did not.

I tried to get the ECU repaired (while already replacing it) and although I did find a place in Tampa that did manage to fix the oxygen sensor issue, the ECU ended up having new problems, including the inability for me to connect to it using a PDU or WDS. I still have that ECU....rather worthless...until someday.

 

Can you see the input reference voltage going to the sensors 5.0 volt " reference " voltage " dither " in voltage value to give the ECU a different set of numbers to calculate the fuel trims and then a different set and then a different set ?

This issue may or may not be his issue but an exercise of learning

Best seen on an old school needle meter

With a bluetooth ELM - 327 reader is the data transfer rate to the reader limiting in it's ability to see the dither ?

 

A setting of the ECM requires a TPS and Oxygen Orientation setup.

If you can communicate with the Engine Module, I would perform the TPS setup and O2 orientation before condemning it.

 

How do I perform a TPS setup?

 

You would need an OBD2 device equipped with Jaguar specific software to do it.

PDU, WDS, VCM1, Mongoose….nothing easy to find or inexpensive….

​​​​​​…..unless….

​​​​​​….you opt for the Chinese clones. They work, but not for long. Once working, and you need a laptop with specific pirated software to get it working, I would limit its use to as needed only.

 

So today I got an used ecu from a 3.2 L, and my suspicion was correct, the ecu in the car was the wrong one, it was for a 4.0 l. However, after I installed the new ecu, the engine ran just like before but the P1777 code was gone. Motorcarman wrote something about a TPS setup, so that's the next thing I will try before I lose my mind. I didn't have the scan tool with me, so I couldn't check if the oxygen sensors were regulating now but I will next week when I have the chance. Does anyone here know if there is someone in Denmark who would be able to perfom a TPS setup?

 

No Jaguar dealers nearby?

how about a “British car specialist”?