I have a small evap leak that I have learned is something that I will have to live with. I have had a bunch of work done to the evaporations system and I don't think the expense of fixing it is worth it or even possible. The leak is tripping the check engine light and I don't like the check engine light. The car is a 2000 xkr and I don't really feel that the check engine light is that important to me. I love that the car has a computer that reads codes and I have a good reader that I use but I don't want the light anymore. It seems like a simple thing to clip the wire from the computer to the light. I know that this is a very sticky subject and I'm not sure if this information should even be in the public domain so if anyone knows about this and could private message me how to do it i'd appreciate it. Thanks!

 

Tis soldered to the board. If you wanted to do this, you need to remove the speedo, open the board, locate the correct led and carefully desolder the leads. You might want to replace it with a regular diode to keep the circuit happy.

To be clear, this will not affect the codes read by you or by any state inspection.

For future reference, it is also probably illegal in your and other jurisdictions to then sell the car in this condition.

 

Hi,
My engine check light was driving me nuts!
i believe the Engine Management Computer has been replaced with one from the next year model. As such it keeps coming up with a code saying that the lambda sensor heater has failed when I don’t believe a 97 XK8 has a lambda heater.
in desperation I removed the speedo and simply slipped a small piece of plastic tube over the light so it is now invisible. I was afraid that if I disconnected the light that it would bring up a warning code in itself.
i must say that the inane complexity of these engine management systems with their proclivity to throw up a fault and put the engine in ‘limp home’ mode is a real nuisance and complete overkill.
does anyone know if there is a way of disabling or permanently over-riding some of the less relevant codes.
It certainly increases a car’s planned obsolescence with issues like you have mentioned
regards
al

 

Yes it does, depending on which side it is, it's a quick check and an inexpensive fix. In fact I will hazard a guess that one of the O2 sensors has been replaced by the unit spec'd for the 98 and on (and had the connector changed as they don't fit) which will work as an O2 sensor but the heater resistance is much higher causing the ECU to think it is open circuit and set the code.

But lets say the O2 sensor had actually failed and stuck low, (which is a $30 fix) - the ECU sets the " very rich" code and turns on the light, it gets ignored or is unseen for long enough and all your plugs get gunged up, performance goes to pot, fuel consumption is horrendous and shortly you will destroy the cat, - a $30 fix turns into a couple of '000.

 

+1

The ECM fitted to the 97 is unique to the X100 and that year, so it's unlikely any replacement will have been sourced from a later model.

The pressures of performance, mimimising emissions and fuel economy mandate tight control of the motor's fuelling, hence the complexity. There are many issues that can cause the warning - not all of them will necessarily be immediately apparent.

I would do some further investigation.

 

Thank you Wight8
i shall investigate
it does appear to be running well although it is currently in dry dock for a failed power steering pump.
why a low km car has failed a ps pump I have no idea, I have generally found them to be rather bullet proof.
Nothing has tested my patience like the XK8. My other Jags have always exceeded expectations but this has been a real problem child in the 10 years I have owned it.
regards
al

 

Most modern Check Engine Lights are NOT tuned ON by the ECM but the ECM tells the INST PK to extinguish the MIL IF all the parameters are met.

It is 'backward' to what most people think.

 

Tis California's fault. Big state, lots of cars sold, cities sitting in bowls surrounded by hills, perfect for trapping smog.

So, California Air Resources Board (CARB) founded in '67 (by Reagan, interestingly) tried to figure out something to do to make the air cleaner. Eventually, they (CARB) invented and required OBD (on board diagnostics) to check/reduce emissions in vehicles in concert with increasing computerization of automobiles, but was too early and it mostly failed from lack of standardization/crappy computers. Around the mid 1990's, just as the XK8 was being designed, everything (worldwide industry, regulation) conspired to make a much more effective and standardized system OBD-II, the system you are burdened/delighted with.

This reduces the emissions of various things, including the EVAP system in the XK8/R to limit gasoline vented into the air and other similar systems. Benefit, the air in Los Angeles now only reeks of ozone from the power lines, not car emissions.

However, important point, these systems are now the law in various places (like every place). There are some exceptions. For example, various US states do not have emissions testing (depending on how polluted they are according to the EPA). My own state, for example, has various counties that have emissions testing (the populous ones) with an exception for cars 20 years old or greater. Even California has an exception for cars from 1975 or before.

The complexity comes from design to the regulations, Jag had to design to those requirements. But the CEL (check engine light, service engine soon, malfunction indicator lamp...) is the consumer face of all that complexity. In the US, EPA regulations require various functions for this lamp. Thus, you can mess with your own lamp in the US, since this is the US, but you can't sell a car to drive on the public highways with this function "messed with" (violation of the Clean Air Act in the US, felony, potentially up to $200,000 fine).

On the other hand, I feel for you and your phantom lambda heater.

 

In the UK and no doubt other European countries, disconnecting the check engine light will cause a fail on the annual inspection. Hence why you can buy on eBay a circuit to light the CEL up, then switch it off again to get the car through its MOT.

Very naughty and as has been pointed out, could easily lead to far more damage down the road.

 

Your car may be low km, but it is still 23 years old!

 

Interesting I have never heard that. Does that not just apply to the monitors needed to pass in Mode 6 on start up (we do not have that test as part of the UK inspection so I am not familiar with it)?
I know that other modules (TCM for example) can request the CEL illuminated as part of a code set and that request is being sent out on the CAN bus - not as far as I know awaiting a direct request from the ECU.

 

Here the logic would be that the MIL/CEL in INST is on unless it is turned off by the CAN messages coming from the ECM through CAN Engine OBDII MIL (and possibly CAN Engine Fault Codes), TCM through CAN TCM Fault Code MIL status (and possibly CAN Transmission Fault Codes), and possibly from ABS through ECM if the ABS token is lost in earlier cars (through 2002).

What I don't know is if TCM indicates a MIL in a condition without ECM MIL, whether that causes ECM to turn the CAN Engine MIL on, or does INST just read the TCM CAN MIL message independently?

 

Looking at the network CAN messages the IP only receives MIL status from the ECM. ABS and TCM warning lights are direct from those modules.

 

This my understanding of the INST PK/ECM relationship.

The INST PK has the Check Engine Light ON as default upon startup.
The ECM commands the MIL OFF if all functions are within parameters upon startup.
The ECM can command the MIL ON if certain conditions are met during vehicle operations.
The TCM or ABS can communicate with the ECM on the CAN bus to command the MIL ON if certain conditions are met.

I have no idea what conditions are required to command the INST PK MIL during vehicle operation except what the DTC guide describes.

It seems to be a logical sequence.

 

I happened to have had the send and receive CAN columns hidden when I looked at my spreadsheet yesterday, so your observation answers the question about potential TCM contribution to P-codes, comes through the ECM.