42 replies to this topic

[Sprocket]

The Lambda value is suspect. Carry out lambda sensor checks................. See pinned topic.

[minidave54]

Cheers Sprocket. I will need to go shopping at the weekend for a digital meter.

I have read it should change rapidly, so does look suspect.

[FlyingScot]

Within 0.5 secs when new

FS

Edited by FlyingScot, 30 June 2017 - 09:44 PM.

[minidave54]

So I have my digital multimeter and tested the Lambda.

Had the car up to normal operating temperature and disconnected the sensor from the main loom.
The meter was set at 200mV range. The readings from the sensor started at 2mV and slowly rose to over 200mV.
With the meter set at 2V range, the reading was 0.234v -- 0.260v. Higher than expected.

I reconnected the sensor in circuit and using pointed probes from the meter had a reading of 0.9v.
Plugging in the Crypton tester the Lambda was showing 703mV.

I'm guessing from these readings my Lambda is shot and needs replacing.

[genpop]

I'm guessing from these readings my Lambda is shot and needs replacing.

not at all, did you already fix the heating problem with your lambda?

[minidave54]

The Lambda heater is now working. But once the engine is up to normal temperature it has no effect on its operation as the heater would be switched off.

[Sprocket]

The Lambda heater is now working. But once the engine is up to normal temperature it has no effect on its operation as the heater would be switched off.

The lambda sensor heater remains on. The PTC heater is turned off when the engine is up to temperature.

[minidave54]

Oops my mistake, i was under the impression that they both turned off.
I will get it checked.

Any thoughts on the Lambda readings i am seeing?
Does it look like i might be needing a new one?

If so, is it advisable to get a Bosch item or are there others that come recommended

[genpop]

Have you already checked the loom.Say 0 ohm from the ecu-socket to the lambda socket and from ecu-socket to cts-socket?

[Sprocket]

With the engine running, you should see the voltage go high to around 500mv and then drop to around 200mv. The time period should be at LEAST once a second (sensor is getting tiered at this point). The voltage numbers are not important as long as they go hi/low.

If the voltage is stuck high, using a hose pipe clamp, gently pinch the fuel supply 'flexi' line (orange), momentaraly, until the engine can be herd to alter tone, too much and the engine will stall. This gives a lean condition and the sensor should read low volts. The lambda sensor is working correctly and the problem lies elsewhere. If the voltage stays high, the sensor may be faulty, or there may be another problem, such as a faulty lambda sensor heater relay.

The best method to carry out these tests is with a diagnostic unit where the voltage reading that the ECU is using can be seen. This is the most deffinative way do determine the lambda sensor operation.

[genpop]

I still recomand my thread within spi code readers. http://www.theminifo...-reader/page-11

 

Here as example you see the graph of  a working lambda sensor and the second picture closed -open loop status.

 

Attached Files

•  lambda.JPG   106.79K   11 downloads
•  loop.JPG   111.9K   6 downloads

[minidave54]

Thank you both for the above information.

When i get the chance i will start by going through the wiring again first to confirm all is good and that the Lambda heater is still working.

I'll then run the engine with the Crypton diagnostics fitted and clamp the hose as suggested and see what readings I get.

[minidave54]

Found time to check Lambda heater and found it was not working. No voltage on loom plug to sensor.

Checked cable through loom from heater relay earth to ECU pin 36, all good. Checked cable from relay output to Lambda plug, all good. ECU plug pin 28 checked to body earth, all good.
Also checked both 12 volt inputs to the relay, again all good.

Earthed heater relay coil by connecting a separate cable to the body and relay operated. With this connected i had the supply to the Lambda heater. It would appear that the relay is not getting the earth path through the ecu

I also checked the PTC relay earth to the ecu pin 6 and found 12 volt on that cable. Again if this relay was getting earthed through the ecu the heater would work.

Is there any way i can check the earth path through the ECU or does it need to be sent away to a specialist company?

[minidave54]

Managed a bit more time on the car today. I have wired in a permanent earth for the Lambda heater relay, so when the main relay is energised the heater comes on.

 

Ran the car up to temperature and connected the diagnostics box again !!! As suggested by Sprocket I clamped the main fuel flex line and the lambda reading did drop slightly to about 500mV before almost stalling.

Would this suggest a good or bad sensor or something else causing the problem with the readings.

 

Something else I noticed was that the stepper position was only reading 13 steps. Will this give a rich mixture?

[minidave54]

Does anybody have any suggestions how to proceed after finding the above issues. Send the ecu away for testing? Replace the lambda? Anything else i can look at or test?