P0452 Symptom and Fix - LotusTalk - The Lotus Cars Community
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post #1 of 2 (permalink) Old 07-30-2018, 03:20 PM Thread Starter
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P0452 Symptom and Fix

I thought this was an interesting enough issue to post to the forum in case someone else encounters it on the V8 (with the latest ECU firmware and fitted with the fuel tank presser sensor that wasn't present on early V8s).

I got a P0452 engine code while driving recently which is a "Circuit Low Input" for the fuel tank pressure sensor. The manual suggests several possibilities for this code from shorted wiring to a bad sensor or ECM issue. However, I also had present a new fuel vapor smell from the LH side of car that didn't take a genius to correlate to the fuel pressure error.

After pulling the side panel off, the problem was obvious: the roll-over valve clear hose had broken in half, letting fuel vapor (and tank pressure) out. Wouldn't you know, it was the only hose I didn't replace back when I did all the evap hoses several years ago. I remember skipping this one because I wasn't sure what the silver addition to the middle of the hose was.

It turns out, the small silver disc in the hose line seems to just be a small restrictor, and it was easy enough to cut out. I used a punch to slide it into the new fuel-rated hose that I used as a replacement for my last remaining piece of clear hose, completing the super-cheap repair with two new hose clamps. I wish I had done that sooner! A few ignition cycles later and the CEL went off.

This is all noteworthy because the Esprit isn't sophisticated enough to detect a difference between a pressure loss, and a problem with the circuit itself. Modern cars will throw a P0455 or P0457 to indicate a large leak in the evap system, but those codes are not part of the Esprit firmware.

The bottom line: If you get a P0452, check for leaks first before you drive yourself crazy troubleshooting wiring or the sensor.

Jake in St. Louis
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Last edited by Add Lightness; 07-30-2018 at 03:27 PM.
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post #2 of 2 (permalink) Old 07-31-2018, 05:44 AM
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Vinyl hose strikes again!!!!!

Atwell Haines
'88 Esprit
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