Tracing and fixing faults in electronic engine management systems
Rob Hawkins visits AJ Fleetcare to inspect their 2006 Nissan Note that has over 180k on the clock and to investigate an emissions-related fault.
The first generation of the Nissan Note (known as the E11) was produced between 2006 and 2013 with a choice of two petrol and one diesel engines. We’re looking at the largest petrol engine (see the August 2021 issue for an Electronic Diagnostics feature on the smaller 1.4-litre petrol engine), which displaces 1598cc and, just like its smaller cousin, uses a fly-by-wire throttle body (there’s no throttle cable).
The Note seen here already had the engine management light (EML) permanently lit on the dashboard. Upon connecting a fault code reader, P0420 had been recorded, which relates to the oxygen sensors – there’s one before the catalytic converter and another after it. However, Alan at AJ Fleetcare wanted to dig a little deeper, explaining that many people often replace one or both sensors, only to find the problem isn’t resolved. And looking at the location of the pre-cat oxygen sensor, in particular, which is accessed from the back of the engine bay, it’s one that nobody would want to replace unless they really had to. Alan used his diagnostic equipment to monitor the voltage output of the oxygen sensors, which helped to determine
whether they had failed. However, it also showed whether the catalytic converter was working because the voltage output measured at the oxygen sensor fitted after the cat (post) should be noticeably lower than the pre-cat (the greater the oxygen that passes over the sensor, the lower its output voltage). It wasn’t, so we suspected the cat was to blame instead of the oxygen sensors.
Typical NISSAN NOTE COMPONENTS
1 The diagnostic port for connecting a fault code reader is on the driver’s side of the dashboard. Release a small plastic access panel (pull it out) to reveal the port and several fuses above it.
2 The 12V vehicle battery is located in the nearside of the engine bay. Connecting a booster pack to it will help to reduce the risk of voltage drops and anomalies when diagnosing faults with the ignition switched on.
3 The earth points for the 12V vehicle battery are secured to the inner wing area (nearside). Check they are securely fitted. From underneath the gearbox, there’s another earth point which, on the vehicle shown here, is slightly corroded.
4 Mounted in front of the 12V vehicle battery is a small fusebox with a table embossed on the top to help identify the fuses and relays inside. There’s another fusebox to the right of here (on the nearside inner wing/arch) and more fuses next to the diagnostic port (see Step 1). See Fault 1 for details about another set of fuses.
5 The air filter housing is in t
