JAG
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| posted on 29/7/25 at 08:37 AM |
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Wideband Lambda - switching
Hello everyone,
I have a wideband Lambda sensor and digital readout on my car. The sensor is in the exhaust.
The instructions for the sensor tell me that I shouldn't power up the sensor until the engine is actually running. The instructions suggest that
when the sensor is powered it is heated electrically and if condensation, from a cold engine, hits the hot sensor it can cause the sensor to fail.
Has anyone ever had this happen?
I ask because it's proving rather difficult to ensure that the sensor is only powered up once the engine is running.
I could put the sensor and display on a separate switch but I'm sure that one day I won't turn it off before shutting down the engine. Then
the next time I start the engine the sensor will be powered up before the engine starts and who knows what will happen 
Has anyone got any experience of this problem?
How do you manage the power to your wideband lambda sensor?
Any idea how I can use the engine to switch on the sensor and digital readout?
Justin
Who is this super hero? Sarge? ...No.
Rosemary, the telephone operator? ...No.
Penry, the mild-mannered janitor? ...Could be!
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SteveWalker
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| posted on 29/7/25 at 08:46 AM |
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Is it really a risk - considering how many cars use the lambda sensor(s) as a signal to the ECU to control fuelling and therefore must have them on at
start up?
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cliftyhanger
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| posted on 29/7/25 at 08:52 AM |
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It is a real issue. OEM cars wait a few minutes before switching teh wideband on. I have an LD wideband and that waits for teh sensor to get hot
before switching on.
Would it be possible to use the ECU to switch it on when the coolant temp gets to (say) 60 degrees?
On the other hand, the vast majority switch on with ignition, and does it cause the sensor to fail more regularly? Maybe... if the sensor is correctly
positioned it will minimise the risks.
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coyoteboy
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| posted on 29/7/25 at 04:53 PM |
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quote:
Originally posted by SteveWalker
Is it really a risk - considering how many cars use the lambda sensor(s) as a signal to the ECU to control fuelling and therefore must have them on at
start up?
Fwiw they don't take notice of the sensor output for fueling at startup, even these days they are usually open loop for 30+ seconds so delaying
the sensor power on is l perfectly possible and normal.
Is it a risk? Depends where you put it in the exhaust. If it's near the ports or just behind the turbo, probably very minor risk. If it's
6ft down the exhaust at the back of a box, there's a much higher risk. I ran mine powered from startup for 4 years before a failure, but it was
right behind the turbo which regularly got to cherry red/translucent so I assume that's what killed it.
[Edited on 29/7/2025 by coyoteboy]
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JAG
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| posted on 30/7/25 at 07:07 AM |
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I have a plan!
My car has fuel injection and a separate switch on the dashboard for the fuel pump. The fuel pump is the last thing to switch on before pressing the
"Engine Start" button.
So I've just purchased a time-delay-relay and I shall wire this to the Fuel Pump switch.
12v Time-Delay-Relay
The Wideband Lambda sensor will go live after a 2 minute delay which will be initiated by the fuel pump switch.
[Edited on 30/7/25 by JAG]
Justin
Who is this super hero? Sarge? ...No.
Rosemary, the telephone operator? ...No.
Penry, the mild-mannered janitor? ...Could be!
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coyoteboy
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| posted on 30/7/25 at 10:30 AM |
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That works! I'd probably drop it to 20 seconds or so though, they really don't like running without power either. Fussy buggers.
[Edited on 31/7/2025 by coyoteboy]
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