Engine light results!

My OBDII scanner arrived today so ive managed to pull the fault codes from my ECU. They were as follows:

O2 sensor circuit bank 1 sensor 1
O2 sensor circuit slow response bank 1 sensor 1
Random/multiple misfire detected
Cylinder 1 misfire detected
Cylinder 2 misfire detected
Cylinder 3 misfire detected
Cylinder 4 misfire detected

Now, i'm presuming the misfires would be due to the O2 sensor fault?

Is it a case of changing the O2 sensor or is there anything else i should be checking first?

Is there a recommended sensor for these trucks i.e denso, ngk, bosch etc?

All those misfire codes are a bit odd.

Reset the errors then run it, see what comes back.

ok, shall i wait until it throws the light up again or just take it for a drive and recheck?

Both would be on my agenda! Start it then test it, see what happens. Take it for a drive then test it see what happens.

Right, i cleared the fault codes and took it for a short drive today. I checked for codes and there were none recorded. However i could feel the engine misfiring. I'm starting to think that something is causing the misfiring and the unburnt fuel going into the exhaust is causing the O2 sensor error code. what do you reckon?

The igniter units are prone to failing on the post 2001 hijets.

It's a box bolted to the rocker cover with 2 big plugs on it.

At the same time I would be tempted to check the plugs, and down tubes from the coil packs.

I would not want to speculate the exact cause of your issue, instead I would find it!

How would i go about testing the igniter unit? Is it covered in the manual?

https://hijet.forumotion.com/t1794-test-your-suspected-faulty-sensors#16953

Most ignition faults on hijets are the rubber down tube things that go from the coil pack to the spark plug.

Thanks for the link HJ.

A bit of an update on this.

I drove the truck round for a bit until i had the engine light come back on and checked the codes again. It threw up both the O2 sensor codes again but no misfire codes this time even though i can feel and hear the engine misfiring.

I checked the ignitor unit and that is metering out fine so i checked the down tubes from the coil packs which you were on about.

I measured the resistance of them and 3 were around about 1 ohm but the 4th, i couldnt really get a reading from, the meter was all over the place like a bad connection so i think it needs replacing.

Whilst i had the coil packs off, i changed the spark plugs for some NGK ones too.

Put it all back together after cleaning all the electrical connections and an earth near the ignitor unit and took it for a spin. It seems a bit smoother (placebo effect?) but is still misfiring.

I've replaced the coil pack tube which i thought was dodgy and the engine is still misfiring. I measured the resistance of the new tube and it was pretty much zero, so as the other tubes measure around 1 ohm is this acceptable or do they need changing too?

What else should i be checking?