Can anyone tell me the resistance values for the heater and sensor on a tree wire Golf MKIII 1.8 ABS engine. I think the can is overfueling so am exploring the probe as a starter.
Thanks Peter
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1-5 Ohms across the two white wires. Check for variable voltage on the black wire 300-800 millivolts fluctuating constantly. Steady output from this wire at either end means a problem. Check carefully the earth connection on the multiplug bracket on O/S inner wing level with the sump.
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Hello Andrew.
Re your response to the original question, could you please advise if the values that you quote are specific to the VW in question or would those values be true of any three wire Lambda ? I have a three wire sensor on a Fiat Uno, the sensor is a Bosch product (as probably, is the one on the VW)
Thank you, Pete.
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Thank you Andrew for the imformation. I am checking the system out because a VW workshop changed the Thottle body bubber gasket the engine feels a little rough ( Harsh ) on the cruise a little like overfuelling. It also is not as smooth under cold choke conditions. Any suggestions would be welcome. Thanks Peter
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Andrew I assume the voltage is measured with the connector off and the engine not running, or if the values you have given taken from a break out connector and the engine running. Many Thanks Peter.
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Resistance measurement done with engine off and sensor disconnected. Voltage reading with engine at operating temp and running. I usually just backprobe the relevant wire with a Snap-On probe down the back of the plug. Doing it that way removes the risk of damaging the mating surfaces of the plug or socket. The specs I gave you are generally the same for most conventional sensors by the way. A four wire sensor will have an earth connection on the fourth (grey) wire.
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Thank you Andrew, thats great information I'll check it out. Regards Peter.
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I have a single wire Lambda sensor on my 95 1.8 Monotronic VW Golf Driver and would like to test the Lambda sensor. If I check its resistance it is very high impedance but the car does not report a fault a the VW agents.
Can onyone including Andrew tell me what characteristics this sensor should have. Thanks Peter
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Hi Peter D,
try this "Technical Information Oxygen Sensor Diagnosis Generic Method" at:
www.forparts.com/o-21.htm
HTH,
CMark
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Thank you, good stuff. Appreciated.
Peter
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You can only check for output on a single wire device, voltage range as above, hot engine. Checking resistance will tell you that the wire is sound to the unit inside. If open circuit it's u/s.
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Andrew thanks for your information. mY problem here is that VW diagnostics say the sensor is OK but a static resistance check says its greater than 2M ohms. Apparantly this single wire sensor on the late ABS 1.8 Golf was a ceramis senosor but I can not find a site that details any resistance for this type of sensor. Many Thanks for any other info you can help me with. Peter
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There is no resistance value for the sensor, it is not that sort of device. It works by generating a small voltage as oxygen passes over precious metals inside it. This voltage is interpreted by the ECU as to whether it needs to richen or lean off the mixture to maintain as near perfect stoichometric ratio (Lambda 1) as possible.
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Thanks Andrew for the information. I was concerned when the resistance was greater than 2 M ohms but the manufacturer confirmed the high impedance is correct infact a lower impedance may have indicated a fouled sensor. Regards Peter
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