Lambda sensor heater supply

[Rascal661]

Hi folks - I'm hoping someone can steer me in the right direction with a lambda sensor issue.

I'm getting "lambda sensor out of range" error codes 44 and 45 for both sensors. I've had a new coil, ignition amplifier, plugs, plug leads, and have removed the plug extenders. Its also had a new stepper motor, recent Airflow meter and the coolant and fuel temp sensor seem to read fine on Rovergauge.

I suspect the heater supply to both sensors is the fault (possibly a break) so intend to bypass the wiring and have run some new wires to test this theory. Can anyone tell me which pin on the relay/which coloured wires at the ecu end provide the heater supply for the lambda sensors?

The car runs perfect at startup, but after a minute or so, runs very rich. It improves under full throttle and above 3000rpm, but car is almost undriveable.

Thanks in advance, oh and its a 1997 Griffith 500.

[Alpha Omega]

Should you be open to some good advice I suggest you find the fault, running wires to bypass a fault is a big step in the wrong direction, 1 faulty wire could be amongst several about to go faulty wires
Bypassing faults often ends in tears or fire and big tears

[Rascal661]

Thanks for the advice. The idea was only as a temporary measure to see if its the wiring to the lambda heater supply which is the fault. If it doesn't work then I'll know that its not a Lambda heater issue.

[Steve_D]

Have you changed the fuel pump relay recently?
Have you fitted the correct type which has 2 pins marked 87.

I suspect the wiring is...
Fuel pump relay
Pin 30 Purple/White (supply)
Pin 87 White/Orange 2 wires. to lambda sensors.
Pin 87 White/Purple to purge valve. Black to fuel pump via immobiliser and inertia switch.
Pin 86 White/green supply to the relay coil.
Pin 85 Blue/Purple coil earth connects to ECU pin 16.

Steve

[Rascal661]

Steve - thanks for your assistance - that's very helpful.

I have the right type of relays and haven't changed them. I did swap both over just to see if it made any difference but it didn't so looks like the relays aren't the problem. My father had suspected a fault in the heater supply wires as we had been getting a lambda error so he had run new wires from the sensors back to the relay, however he has put them into the green and white wire at the relay (wrong one) so the chances are the sensors aren't getting the right voltage at all and will be misreading.

Will revert to the original wiring at the weekend and see if it improves - I suspect the lambda error was a symptom of something else, and nothing to do with a wiring fault at all.

Thanks again

[blitzracing]

You need 12 volts on the red lambda heater wire- but its only there when the engine is running as it uses the same supply as the fuel pump. You say RoverGauge is fine- it wont be if the 12v feed is missing, as these resistive probes need the 12v feed to produce a switching output- so you are likely to see massive short term fuel trim (adding fuel) as the ECU tries to get the probe to switch, before it throws the fault code after some minutes.

Have a read:

http://www.g33.co.uk/img/fuel/14cux_fault_finding....

[Rascal661]

Thanks Blitz - what I meant was that the Rovergauge readings for the coolant and fuel temp sensors were fine, not the lambda sensors. They are showing an off the scale short term fuel adjustment. Thanks for the link - I still have much to learn, so that will be helpful.

[Rascal661]

Well - the Griffith is fixed! both lambda sensors were duff and needing replaced. I originally got a lambda error code due to a misfire caused by a loose electrical connector on one of the injectors, which made the sensor read too lean so the ecu compensated for by increasing the fueling. We ran the car for a while thinking it was an ignition fault before I finally spotted the problem with the connection to the injector. It seems that with it running so rich it has poisoned both lambdas. So running perfectly again and with the original wiring and no need to bypass anything. I can now get now get back to enjoying TVR ownership again...finally.