Jaguar X-Type alternator fault

**alexs307** · 18th April, 2011, 10:50 PM

Hello, DK friends.
I am asking for help as I am not able to find a proper solution for my problem.
The car concerned is a 2002 Jaguar X-Type, petrol engine 2.0 V6. Battery warning light showed on the dash 1 week ago, after several tests we have found out that the cable between the generator and the battery was the problem. We replaced it, but the generator kept charging 16volts. So we replaced the charging relay, but we weren't able to find an original one, Denso 126000-3430, so we used a replacement from an unknown brand. It seems that the new part fitted is not fully compatible with the car's ECU. Although the charging problem is solved, we are getting a permanent fault in ecu DTC memory, and car goes into limp mode, meaning normal power, but engine cooling fans running on max speed all the time.

PCode is P1146, meaning Generator C line low input.
From wiring diagram, the connections between ECU and generator are:

a. one wire called GENERATOR FIELD (has 12V when we switch on ignition - measured on the generator connector not connected into plug)
b. one wired called GENERATOR LOAD (has 12V in same conditions as mentioned above)
c. one wired called GENERATOR CHARGE (has 0Volts in same conditions mentioned above, but:
- if we plug the connector into the new charging
relay, there is same voltage : 0Volts
- of we plug the connector into old charging relay,
there is 12V when ignition is switched on

So this is the problem, the aftermarket charging relay does not communicate via GENERATOR CHARGE wire with engine ECU.
My questions are:
- what exactly does this signal (Charge-line) represent?
- how can I fool the engine ECU in this case to get rid of P1146?

I already tried connecting the Charge-Line to 12V, and the fault switched to P1245, if I remember right, meaning Generator C-Line high input.

Any help is apreciated. Thanks in advance.
Regards,
Alex.

**Xram** · 18th April, 2011, 11:57 PM

This is fords junk smart charge system I suspect you have one of 2 problems first broken/short wire at engine block trace the system back also check the fuse for the smart system may not be blown but if corroded will give a high resistance.
When you remove the smart charge 3 pin plug from the back of the alternator it reverts to a conventional alternator if you do.

You will need a scope to check the smart charge system
Pin 1 ... Alternator Feedback
Pin 2 ... Alternator Load Request FROM ECU
Pin 3 ... Reference Voltage 12 VOLTS +
pin3 must be the same as the battery voltage

Sounds to me though that there is no issue with your old relay haven't worked on the jags but it is a common ford fault and there is a repair loom for the smart charge system for around ?10.00 check the wires normally within 6-10 inches from the connector.

It has a smart alternator for two reasons one it has a Silver/Calcium battery. Two the cars ecu can ask the alternator for 16volts (higher than most) as and when required. the reason the fans run is the ecu doesnt know what voltage is coming out the alternator so it assumes its faulty overcharging so runs the fans at full speed to use up the possible extra power. Also you may find heated screens and a few other things no longer work as the ecu wont allow them to run.

**alexs307** · 19th April, 2011, 07:14 AM

The generator connector has 4 pins:
1. +12V via F82 fuse, in junction box under dashboard - fuse ok, not corroded
2. FIELD wire
3. CHARGE wire
4. LOAD wire

With old relay, no error occured on ECU, but generator kept charging 16v, and after a while suddenly dropped at 12V. I switched it back even after cable repairing,and same result, also battery light was present on dash panel. I plugged generator connector back into old relay, even if it's not actually attached to generator - no error, and when I switch on ignition, I have 12V going out of relay via CHARGE wire to ECU. With afermarket relay, there is no output voltage on this CHARGE wire. I put 12V on the wire from another source, error dissappeared for a while but after 5 min, it switched to P1244 (generator c line high input), instead of old P1146(generator c line low input).

So it is obvious the aftermarket relay doesn't know about C line. My question is what kind of signal should I bring onto the C wire from an external source in order to fool the ecu and get out of stupid limp mode- fans running on maximum speed?

I checked all wires between generator and ECU - everything ok.