Fuse 34 - part deux
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Does anyone have a wiring diagram for the circuit off fuse 34? All it says on the fuse box cover is Fuel pump ande O2 sensor.
Having replaced my fuel pump I yet again blew the fuse today (luckily right in front of Tim Horton's). Replaced the fuse immediately and it would blow again when the engine was started. Now here is the interesting part - replaced the fuse with the engine off, shorted out the DME relay so the fuel pump would run and the fuse didn't blow!
The wife suggested disconnecting the "oxygen sensor thingy" (her words) and see if that would work. Engine ran fine and made it all the way back home. ACtually, it seemed as if the idle was alot smoother too....
Is it possible for an O2 sensor to short out? I notice there are 3 wires on the sensor - I get a resistance of 7 to 9 ohms (at idle - as engine warms up the resistance goes up) between the two female connections on the sensor. What is the third wire for?
Having replaced my fuel pump I yet again blew the fuse today (luckily right in front of Tim Horton's). Replaced the fuse immediately and it would blow again when the engine was started. Now here is the interesting part - replaced the fuse with the engine off, shorted out the DME relay so the fuel pump would run and the fuse didn't blow!
The wife suggested disconnecting the "oxygen sensor thingy" (her words) and see if that would work. Engine ran fine and made it all the way back home. ACtually, it seemed as if the idle was alot smoother too....
Is it possible for an O2 sensor to short out? I notice there are 3 wires on the sensor - I get a resistance of 7 to 9 ohms (at idle - as engine warms up the resistance goes up) between the two female connections on the sensor. What is the third wire for?
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Originally Posted by frankvan
Is it possible for an O2 sensor to short out? I notice there are 3 wires on the sensor - I get a resistance of 7 to 9 ohms (at idle - as engine warms up the resistance goes up) between the two female connections on the sensor. What is the third wire for?
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I have the diag software and it showed 24- oxygen sensor failure when i had it disconnected. Other than that no errors. However, if it is a problem with the heater circuit it might not show up as an error (the software only looks at the sensing function?). When hooked up to the software the O2 Sensor field reads between 50 and 90 (millivolts?)
Upon inspection of the oxygen sensor the inner heat shield appears to have corroded one of its mounts and shifted up a bit so as to rub against the outer housing of the sensor. Could that cause a short? The rubbing was enough to polish the heat shield in that one area... I have since bent the heat shield away so that the sensor is not touching anything again. Not sure if I want to remove that heat shield altogether though as the lower spark plug wires are quite close to it. Also noticed searching the forum that there are pictures of a small shield around the sensor which mine doesn't have. (maybe that would have prevented this all from happening!)
Oh, and car is an august 89 build (C4).
Thanks
Frank
Upon inspection of the oxygen sensor the inner heat shield appears to have corroded one of its mounts and shifted up a bit so as to rub against the outer housing of the sensor. Could that cause a short? The rubbing was enough to polish the heat shield in that one area... I have since bent the heat shield away so that the sensor is not touching anything again. Not sure if I want to remove that heat shield altogether though as the lower spark plug wires are quite close to it. Also noticed searching the forum that there are pictures of a small shield around the sensor which mine doesn't have. (maybe that would have prevented this all from happening!)
Oh, and car is an august 89 build (C4).
Thanks
Frank
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Originally Posted by frankvan
if it is a problem with the heater circuit it might not show up as an error (the software only looks at the sensing function?).
Originally Posted by frankvan
When hooked up to the software the O2 Sensor field reads between 50 and 90 (millivolts?)
Originally Posted by frankvan
Could that cause a short? ... I have since bent the heat shield away so that the sensor is not touching anything again.
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Thanks Jason,
i haven't had a chance to drive the car yet - haven't had the courage! I'm going to try and get out this afternoon if and when the rain stops and the roads dry up. I'm also going to see if I can get an ammeter (fused) hooked up and find out how much current is being used during operation with and without the o2 sensor connected.
Using a bench ammeter the fuel pump showed a draw of only 1 amp with no load and peaked at around 2 amps with a load. That shouldn't blow a fuse...(rated at 15 amps).
Also took the cover off the DME relay - it's just two solenoids! The top one appears to be the one for the fuel pump. What does the lower one connect to? (The O2 sensor shouldn't require a relay, should it?)
i haven't had a chance to drive the car yet - haven't had the courage! I'm going to try and get out this afternoon if and when the rain stops and the roads dry up. I'm also going to see if I can get an ammeter (fused) hooked up and find out how much current is being used during operation with and without the o2 sensor connected.
Using a bench ammeter the fuel pump showed a draw of only 1 amp with no load and peaked at around 2 amps with a load. That shouldn't blow a fuse...(rated at 15 amps).
Also took the cover off the DME relay - it's just two solenoids! The top one appears to be the one for the fuel pump. What does the lower one connect to? (The O2 sensor shouldn't require a relay, should it?)