Evening,

The story behind this vehicle is that the EML warning light came on a few weeks ago and then failed the MOT emission test a few days ago.

Now I think I have solved the emissions issue but have published it here in case it bears a relation to the EML problem. Without diagnosis, the garage suggested that the HO2 sensor be replaced to solve the 2 problems. It didn't. The sensor is NGK/NTK Broadband sensor. From memory, It failed because the Lambda reading was slightly too high although the CO was a pass but very marginal. I found the CO at 0% on both natural and fast idle with good HC's but O2 was about 2.8% on natural idle and lower on fast idle. On inspection, I found a blowing exhaust joint on the middle box which is the reason for high O2 and subsequent high Lambda value. Customer has been advised to get that repaired and hopefully it will pass.

The second problem on which I am stuck are the fault codes as follows: They all relate to the heating element of the Broadband HO2. PO030 - Bank 1 Sensor 1, PO036 + PO141 Bank 1 Sensor 2. There are 5 wires to the sensor and read as follows: 2 heater wires = 2.95v (blue and yellow), Earth wire = 2.95v (Black), Measurement cell = 2.5v (grey), Pump flow = battery voltage (white). Now I would have thought the earth wire would have been below 0.25v and did consider stuffing it to earth but thought I should exercise caution on a new sensor which cost the customer about £150!

So, I would be grateful on what you think about these voltages and how I should remedy the situation. Apologise for long post but needed to make sure you have all relevant info.

Regards

Pete M