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CAT problem

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Hi all,

I recently replaced my exhaust box for a Lotus sports box on my V8 and in the process saw that the ceramic in the nearside CAT is loose. It looks like its been banging around a bit and taken some damage from the Lambda sensor.

My question is this: will this damage the sensor? Is it safe to drive around until I get a replacement?

I'm a bit stuck for cash as well so also considering just getting a standard replacement from SJ for the one side. Is it always necessary to replace both at the same time? Or should I just go for "broke" :/

cheers up front


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You should be ok for a while cats normally either go on melt down due to misfire hence uburnt fuel going down the exhaust pipe hitting the hot cat and melting the ceramics and clogging the honey cone structure up which results in the cylinders not been able to expel; the exhaust gases properly i.e you loose power, Or genral wear and tear like yours when the internals simply break down, this should not damaage the lambda probe and should be fine for driving for a while, you should replace as soon as you funds though.

Regards danny

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Hi Danny - Cheers for that. With the new sports pipe you can hear the thing bobbling around and that made me wonder if it would handle another 500 miles or so. I guess it should run a bit better after so looking forward to that!

thanks again


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I was informed by my mechanic (well known by the forum) that the car would be ok to run without the ceramic as you mentioned Danny.

So last weekend I decided to get the ceramic out but the day before I made a somewhat brisk start from the lights and the check engine light came on.

The following day I pull the silencer off and see the ceramic is GONE. Checked that the silencer wasn't blocked and put it back together.

Since aquired the ODB11 reader thinking reset the ECU but the light comes back on after just a few seconds. Fault codes are the usual suspects: P0444 and P1411

The sensor readings appear to be ok but Oxygen sensor monitor and Oxygen sensor heater monitors are logged as "Not Completed".

Does this look like the sensor got shot in the process?

Please bear in mind this is my first use of the ODB11 reader..

many thanks


Connection details

OBD standard reported OBD I

Battery voltage 14.1V

Diagnostics protocol AUTO,ISO9141-2

Fault codes

Fault code Code status Code type Definition

P0444 Stored Generic Evaporative Emission Control System Purge

Control Valve Circuit Open

P1411 Stored Mfr-spec Code definition not known - please refer to

car service manual

Freeze Frame data

Fault code Sensor Value

P0444 Sensor values:

Calculated Load 1,96 %

Coolant Temperature 74, C

Short Term Fuel Trim Bank 1 0, %

Long Term Fuel Trim Bank 1 0, %

Short Term Fuel Trim Bank 2 0, %

Long Term Fuel Trim Bank 2 0, %

Intake Manifold Pressure 36 kPa

Engine Speed 863 rpm

Vehicle Speed 0 km/h

Fuel System 1 Status Open Loop

Fuel System 2 Status Open Loop

Onboard test results

On-board test Current status

Misfire monitor Completed

Fuel System monitor Completed

Components monitor Completed

Catalyst monitor Not supported by car

Heated Catalyst monitor Not supported by car

Evaporative System monitor Not supported by car

Secondary Air System monitor Not supported by car

A/C Refrigerant monitor Not supported by car

Oxygen Sensor monitor Not completed

Oxygen Sensor Heater monitor Not completed

EGR System monitor Not supported by car

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Hi Charlie,

According to the Service Manual the error code P0444 should only be present on USA vehicles.

Both errors are circuit related and use fuse B7. Have you checked this fuse? Worst case is that you have an ECU problem, as both errors mention the possibility (Hopefully it's not the ECU).

P1411 Solenoid Open Circuit

Description: This is a circuit check, to see if the solenoid circuit is open

Malfunction Criteria: Logic level high

Secondary enable conditions: Solenoid state on

Disabled by faults: None

Time required: 1 sec

Potential failure modes: - Connectors

- Wire open circuit (fuse B7 blown?)

- Solenoid missing

- Solenoid faulty

- ECM input circuit failed

Limp home: None

PO444 Purge Control Valve Circuit Open

Description: Circuit check

Malfunction Criteria: Logic level low

Secondary enable conditions: Purge valve state off

Disabled by faults: None

Time required: 1 sec

Potential failure modes: - Connectors

- Wire open circuit (fuse B7 blown?)

- Relay missing

- Relay faulty

- ECM input circuit failed

Limp home: None

Note: This is only available in USA vehicles

Edited by peter_england99

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all that *fuse 7* thing reminds me on what happens to my car with the old sensors. The o2-sensor heathercircuit failed. And therefore an high amp was gone over the fuse every time. As i unplugged the O2-sensor the problem was gone, other ways the CEL was set every time ignition key was turned in position 'on' .

I think all V8-GT cars are production after the *revised harness*project, and the B7 fuse does hold also o2-sensor heater circuit on my car. The workshop book is not fully correct on that thing. We have spoken about that problem some time ago in this board... .

You can ask Marcus Freudhoefer ! I have spoken with him about those incorrect documentations. The fuse sheme in the owners handbook/workshop-book mentioned 4 cylinder engine cars. Bud it is the wiring sheme on the V8's !

Look into page 14 section ML. Left hand lower edge on the side: *B7* -evap. purge soleniod, O2-heater & wastegate solenoid. All that for the 4 pot. Bud for the V8 it says: Ignition controls !?

Edited by G

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Hey Carly, i did that 'disconnect' thing to verify that it is related to the sensor/heater element in the sensor. All my o2-sensors are still the old stock from '98 , bud one of those is fallen apart now. In the time the rust killed the main part (with the socket/spanner face) the contacts for the heater element get shorted to ground/to the other systems. Therefore an uncontrolled high amp level was on along the circuit, every time the ignition key was turned 'on'. As in that key-position voltage normally goes to the heater-circuit to make the o2-sensor *ready to go* (you can call it o2-sensor preheater function..). I have after that changed all positions of the o2-sensors -namely all good ones to the front and all with faults/internal broken heater wirings/or totally rusted contacts to the rear end of the cat pipe.

I can make pictures of that faulty sensor tomorrow, as i think none would believe what i say: bud those can get really rusty and those corrosion will gone deeper and deeper until it reaches the ceramic main parts.. .

If you get sparks than it does indicate an high amp load. does the fuse blow if you turn on ignition ?

So first undo the connectors for the o2-sensors. Turn on your ignition and see if that fuse B7 is blown now. Than connect one after an other and see what happens if you turn the ignition on. All i can say is that we have spoken about the *only available in US* related to Evaporative & Wastegate control in this board, and the consensus was that our GB/Europe cars from the late 90th do not have that stuff actually. So my thought was there must be an other 'thing' in that circuit. And as i have seen that the description in the workshop-book said (for the 4 pot of course..) Evap- & wastegate control And o2-heater, it tried those... .

In short words: under the cable/contact cover (red area) was all corroded on mine. The broken/free cable ends get contact to the cover (that is nothing else than an 'shortcut' into the wrong circuits..). And the part with the 'active' ceramic was still in the exhaust. It all starts with an slight sign of rust along the base of the cover, than the rust gets the volume it needs and the cover lifts up. After that, together with vibration/heat and more ambient water the contacts fail.. .

Edited by G

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rust is the enemy, in every case... . So avoid that it turns out this way (see attachment)

Mentioning your question, all I would say is that the ceramic powder of the disintegrated cats will block your sensor slots (in the cover for the active part that gets into the gas flow) . The result is an *sensor not ready/implausible signals* code. And the metal ring of the old monolith can dance around, that makes silly noise and he can knock onto your sensor. So i would say: open your catalyst along the weld line an replace the internals with cheap metal-race-cat inserts, or if you want to run without any cat-just remove all loose parts inside !

good luck for the future..

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