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mrfirepro

Member Since: 06 Nov 2020
Location: kent
Posts: 228

1996 Defender 90 300 Tdi HT Bonatti Grey

Fault code P121C-00 Cylinder balance - Injector leaking

I'm experiencing the above code, which comes in at around 3000 RPM then goes into limp mode.

I then stop and start and alls good until 3000 rpm again. I've checked as many of the electrical connectors as possible, I read on a Transit forum that this code sometimes is the VCV. Before I go delving into replacing injectors, just wonder if there is any advice on options.

TIA

2nd May 2023 5:37pm

Crofter

Member Since: 19 Feb 2015
Location: Peterhead
Posts: 169

2009 Defender 110 Puma 2.4 USW Baltic Blue

I have and probably still have the same problem.
P121C I was told by someone on here is a Ford code. Which is either an open circuit or short circuit injector.
I bought an ancel plug in device and reset the Faulk code which disappeared for about 1000 miles.
However it started going into limp mode at the weekend. However the 3000 revs bit is not failure point now.
I am thinking about changing injectors soon.

3rd May 2023 8:40am

mrfirepro

Member Since: 06 Nov 2020
Location: kent
Posts: 228

I've decided to remove the injectors and have a look. Interestingly the copper seal rings on 1,2 and 4 were still a copper colour and in good condition. The copper seal for injector number 3 was almost totally black.

Click image to enlarge

I'm no expert but going to replace all the seals and rocker cover gasket put back together and see what happens.

I've only spent around £90 on a seal kit and a seat tool.

I was however amazed at how little pressure there was on the stretch bolts that secure the injectors, I wish I had measured the torque but it definitely felt like I could have undone them by hand.

The truck has done 130,00 miles but I do service it every 5000 miles.

3rd May 2023 9:59pm

Crofter

Member Since: 19 Feb 2015
Location: Peterhead
Posts: 169

That’s interesting, can I ask where you got the copper washers and the tool.

4th May 2023 10:33am

mrfirepro

Member Since: 06 Nov 2020
Location: kent
Posts: 228

it's now been a couple of weeks and 500 miles and the fault has not returned so hopefully all is good.

All I did was replace the copper washers and properly torqued the injector retaining brackets. I suspect that the bolts had come loose over time as they took almost no effort to remove.

I bought a kit off Amazon which included the injector seal washers, the green O rings, rocker gasket and new stretch bolts.

18th May 2023 8:04pm

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