Lambda sensors dead?
Discussion
Good morning,
On my 4.5 Cerb both lambdas were stuck on 0.00v . I figured this was due to them both dying, as apparently they do. So I ordered 2 new ones.
Installed last night and they both read 0.00v. Checking over this morning with a temperature gun and when cold I'm getting 13 deg C. With ignition on I get up to 27 deg on the RH sensor and 15 deg on the LH sensor. This is measured at the nut where it bolts into the exhaust. With the engine off and the ignition on I am getting readings (0.1 ish) yet as soon as I start the car they both go to zero and the adaptives start doing their thing.
I've read about issues with voltage at the heating element, is this something people have solved? I'm flat out finding the things on the wiring diagrams.
Has anybody else had this issue?
On my 4.5 Cerb both lambdas were stuck on 0.00v . I figured this was due to them both dying, as apparently they do. So I ordered 2 new ones.
Installed last night and they both read 0.00v. Checking over this morning with a temperature gun and when cold I'm getting 13 deg C. With ignition on I get up to 27 deg on the RH sensor and 15 deg on the LH sensor. This is measured at the nut where it bolts into the exhaust. With the engine off and the ignition on I am getting readings (0.1 ish) yet as soon as I start the car they both go to zero and the adaptives start doing their thing.
I've read about issues with voltage at the heating element, is this something people have solved? I'm flat out finding the things on the wiring diagrams.
Has anybody else had this issue?
Have you checked for:
1. Any blown fuses. Unlikely if everything else on the car works but worth giving every possibility of having power before point 2.
2. Checked the sensors are actually getting 12v with a multimeter on the plugs?
3. Checked earth?
4. Checked continuity from the sensor plugs to ECU?
1. Any blown fuses. Unlikely if everything else on the car works but worth giving every possibility of having power before point 2.
2. Checked the sensors are actually getting 12v with a multimeter on the plugs?
3. Checked earth?
4. Checked continuity from the sensor plugs to ECU?
You have a problem if you're registering a temp rise with the engine not running. This is because the lambda heaters are only powered when the fuel pump is running, so unless you have 1) bypassed the ecu control of the pump and have it running constantly or 2) are cycling the ign on and off all the time to enable the pump prime you shouldn't really see any rise at all in temp at the sensor as it will be powered off unless the engine is running.
Also there are many reasons for a lambda to read 0volts, only one of which is failed sensor.
post a video of your diags screen with engine running, or screenshots .. also tell us what the kg/hr is through your throttles.
Also there are many reasons for a lambda to read 0volts, only one of which is failed sensor.
post a video of your diags screen with engine running, or screenshots .. also tell us what the kg/hr is through your throttles.
I suffered some lambda learning last year - https://www.pistonheads.com/gassing/topic.asp?h=0&...
The long and short of it is, if a TP is set too low, the lambda will appear dead.
The lambda’s are narrow band, so my understanding (could well be wrong) is that they only report a high voltage when they sniff a stoichiometric AFR.
The long and short of it is, if a TP is set too low, the lambda will appear dead.
The lambda’s are narrow band, so my understanding (could well be wrong) is that they only report a high voltage when they sniff a stoichiometric AFR.
The lambdas have 11.8v at the plug, with no fuel pump running. I haven't checked for continuity to the ECU yet.
The fuses are all good!
Imran, what TPS setting at idle did you end up with? I'm currently at around 14.5%. I did briefly try around 18% whilst idling with no luck. Maybe I need to try a higher TPS and actually drive it till it's hot.
The fuses are all good!
Imran, what TPS setting at idle did you end up with? I'm currently at around 14.5%. I did briefly try around 18% whilst idling with no luck. Maybe I need to try a higher TPS and actually drive it till it's hot.
Edited by mrniceguy351 on Friday 13th May 19:45
mrniceguy351 said:
The lambdas have 11.8v at the plug, with no fuel pump running. I haven't checked for continuity to the ECU yet.
The fuses are all good!
Imran, what TPS setting at idle did you end up with? I'm currently at around 14.5%. I did briefly try around 18% whilst idling with no luck. Maybe I need to try a higher TPS and actually drive it till it's hot.
I do believe I had to get to above 18% for the lambda to finally react. I don’t think you have to drive it (to warm up), but hey, it’s a TVR, anything is possible!The fuses are all good!
Imran, what TPS setting at idle did you end up with? I'm currently at around 14.5%. I did briefly try around 18% whilst idling with no luck. Maybe I need to try a higher TPS and actually drive it till it's hot.
Edited by mrniceguy351 on Friday 13th May 19:45
Off topic but could be on topic
If the engine revs were taken to above alternator cut-in speed before the engine was allowed to idle at 700 RPM there could be a charging problem or something wrong with the diagnostics software,cable or circuit
Battery voltage is too low, alternator is not charging if the reading below is correct
If the engine revs were taken to above alternator cut-in speed before the engine was allowed to idle at 700 RPM there could be a charging problem or something wrong with the diagnostics software,cable or circuit
Battery voltage is too low, alternator is not charging if the reading below is correct
You need to be aiming for a 1000rpm idle, and more fuel/less air, until the adaptives run under 5 -/+. 1000rpm idle will help with alternator charge.
OP, have you read any of the howtos on setting the car up? Do you understand that the adaptives showing in the 30s is a bad thing, and as close to zero as possible is the target? Your balance is way out in favour of air over fuel.
OP, have you read any of the howtos on setting the car up? Do you understand that the adaptives showing in the 30s is a bad thing, and as close to zero as possible is the target? Your balance is way out in favour of air over fuel.
mrniceguy351 said:
Yes, I do understand that is bad. That's why I'm asking about it here.
Ok, so have you tried moving the TPs so that you're adding fuel? Your engine is begging for fuel at the moment. I don't mean opening the throttles, just move the TPs on the spline, until you see the adaptives lower. I'd try moving them max the other way, try and see if you can get the engine running rich instead of lean.Good luck.
mrniceguy351 said:
The lambdas have 11.8v at the plug, with no fuel pump running
Charging is ok thenIf your car has the Porsche fusebox fitted
See fuses 34 and 35
Without checking but......, I would expect an ignition supply to the sensors from fuse 35 with ignition on and the sensors heaters to be supplied from fuse 34 when the fuel pump is running
The 11.8v at the plug will very likely be the ignition supply from fuse 35
Ooooh, nearly forgot to ask, are sensors of the 3 or 4 wire type?
and
Surely the voltage needs to be above 12 for accurate diagnostics
Ok then
Just a thought, before you possibly delve deeper and miss something obvious
The sensors supply voltages can only be measured with the sensors connected
Now here's the tricky part, you will need to make, beg, borrow or steal some purpose built cables to break out of the circuit to measure the voltage with sensors still connected
or
Measure what current the sensors are drawing and load the sensors supply cables at their disconnected plugs using bulbs that will draw a similar current
If you probe the insulation of the cables they will corrode over time unless properly insulated once testing is finished
Same goes for checking the negatives
Just a thought, before you possibly delve deeper and miss something obvious
The sensors supply voltages can only be measured with the sensors connected
Now here's the tricky part, you will need to make, beg, borrow or steal some purpose built cables to break out of the circuit to measure the voltage with sensors still connected
or
Measure what current the sensors are drawing and load the sensors supply cables at their disconnected plugs using bulbs that will draw a similar current
If you probe the insulation of the cables they will corrode over time unless properly insulated once testing is finished
Same goes for checking the negatives
Edited by Polly Grigora on Saturday 14th May 11:53
mrniceguy351 said:
The sensors are three wire type.
I have had the TPS set at 12%, 25% and multiple values in between.
How is the car driving? Can you go for a drive and then post a csv of the logs?I have had the TPS set at 12%, 25% and multiple values in between.
I'd suggest setting up from scratch, and open the throttle to 1200rpm idle whilst doing so.
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