Restricted Performance..and 500km drive! Transmission warning light on.Major problem?

in case anyone was interested, the LR Indie found the issue...we had recently completed the Gibb River Road, and went through a number of water crossings. Whilst the maximum we went through was 60cm in depth (for a split second), the Indie told me he had seen several RRS that had done the gibb come in with the same issue. Apparently its the back pressure valve in the exhaust which seizes up...and the only way to correct it and ensure it doesnt go into limp mode is to replace the centre section of the exhaust. Just over $5k later it was fixed!

Cheers,

Chris

The Gibb is on my bucket list, so that's good to know!

Is your vehicle fitted with a DPF?

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Originally Posted by Graeme

Is your vehicle fitted with a DPF?

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Yep...and that had issues last year and went into limp mode because of it. This was a different warning light though. why do you ask?

I wondered if that back-pressure valve, of which I've not heard before, is really one of the 2 DPF pressure sensors, although the fault codes were unrelated to DPF issues so probably not.

OK,, I'll ask.... why do we have a back pressure valve?

and please dont say it closes and creates back pressure...

is it a regen thing?

Back pressure where DPFs are concerned is detected by the difference in pressure as provided by the pre and post DPF pressure sensors and quite often the DPF has to be cut out to be cleaned or replaced if no cleaning service is available. I suspect it was a misunderstandng in the terms used but I'm still at a loss as to why the faults weren't DPF faults, unless the code reader couldn't read emission faults and that the found faults were another issue.

Edit: The tool is a Gap IIDtool so not a fault with the code reader.

So.. the two sensors match until the DPF is clogged enough to un-match them, then a regen occurs,, Yes?

The DPF is restrictive even when not blocked so a difference in pressures is expected, but too big a difference triggers a regen.
Ensure oil changes are frequent if regens are frequent, including restarted regens when the last one didn't complete, as oil dilution with diesel occurs with every regen which reduces the lubrication ability of the oil.

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Originally Posted by Graeme

Back pressure where DPFs are concerned is detected by the difference in pressure as provided by the pre and post DPF pressure sensors

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Just a data point but on my D3 the DPF pressure sensor was a single differential sensor rather than pre and post individual sensors.