0.0 Volts at Bank 1 Oxygen Sensor Issue - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 6 Old 11-02-2016, 08:46 AM Thread Starter
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0.0 Volts at Bank 1 Oxygen Sensor Issue

Hey all,

I have a 1990 GT that is running very rich and seems to stay in open loop. I had a shop verify that the Bank 1 02 sensor is reading 0.0 volts at all times. I've verified my grounds, resistance values of the ECM harness and pin 46 of ECU, replaced the passenger side O2, and replaced the O2 harness. TPM and MAF appear to be functioning as they should, but MAF voltage at idle seems a little high... Around 0.9-1.1V. Is there anywhere else I could look or any potential causes that could be causing the 0 V reading at the sensor? FPR appears to be functioning well too.... Just scratching my head over this one...

Forgot to mention that the bank 2 O2 sensor is working properly...

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post #2 of 6 Old 11-03-2016, 10:36 AM
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What is pin 46 of the ecu?
Do you have a electrical diagram showing the o2 sensors and pin out to the ecm to post?

I would maybe check continuity at the pin on the ecu that goes to the 02 sensor in question and to ground (Guessing without looking at the diagram). Do this with ignition off. Your looking to find out if you have a complete circuit.
If continuity is infinite, you have a break somewhere in the circuit. If you are seeing zero resistance, you have a short in that circuit somewhere.

Either do above, or check voltage at the wire right at the ecm (whatever pin number and wire colour that is) that goes to the o2 sensor while the vehicle is running. Any voltage there?


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post #3 of 6 Old 11-03-2016, 03:09 PM
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Pin 46 is a signal return gnd for your TPS, ECT, ACT, egr, and BP.
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post #4 of 6 Old 11-03-2016, 08:44 PM
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Originally Posted by W72 400 View Post
Hey all,

I have a 1990 GT that is running very rich and seems to stay in open loop. I had a shop verify that the Bank 1 02 sensor is reading 0.0 volts at all times. I've verified my grounds, resistance values of the ECM harness and pin 46 of ECU, replaced the passenger side O2, and replaced the O2 harness. TPM and MAF appear to be functioning as they should, but MAF voltage at idle seems a little high... Around 0.9-1.1V. Is there anywhere else I could look or any potential causes that could be causing the 0 V reading at the sensor? FPR appears to be functioning well too.... Just scratching my head over this one...

Forgot to mention that the bank 2 O2 sensor is working properly...
How did you verify your grounds?

resistance value of harness? what........I single strand of wire will show GOOD, but will NOT carry current and will become a voltage drop.....

You have to perform voltage drop tests ON ENERGIZED LOADED circuits.

search on how to do it. and learns it.

I will give you two quick possible reasons for 0 volts on the 02, that works

1) open
2)short to ground

both may NOT show up on a resistance test, with a common OHM meter.

89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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post #5 of 6 Old 11-07-2016, 12:56 PM Thread Starter
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How did you verify your grounds?

resistance value of harness? what........I single strand of wire will show GOOD, but will NOT carry current and will become a voltage drop.....

You have to perform voltage drop tests ON ENERGIZED LOADED circuits.

search on how to do it. and learns it.

I will give you two quick possible reasons for 0 volts on the 02, that works

1) open
2)short to ground

both may NOT show up on a resistance test, with a common OHM meter.
Updated below and good points....

  • I'm not sure how the shop was able to get a voltage on 1 bank, as I'm seeing 0.0 volts at pins 29 and 43 with the car idling.
  • Measured 1.5 ohms resistance from the driver's side HEGO harness to pin 43 - HEGO unplugged
  • Measured 1.6 ohms resistance from the passenger's side HEGO harness to pin 29 - HEGO unplugged
  • Measured 12 volts to both HEGO sensors with them unplugged (i.e. orange wires) and the ignition on
  • Measured 3.0 ohms resistance from chassis ground near ECU to pin 49
  • Less than 2.0 ohms resistance from chassis ground near ECU to pins: 16, 20, 40, and 60

From the above points, I'm not seeing an open circuit. I do need to see if I'm shorting to ground. This was an issue I had with a 442 I restored and kept me busy for some time. I'll check to see if I have voltage to any of those grounds with the vehicle running. Any other ideas or suggestions?
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post #6 of 6 Old 11-07-2016, 05:37 PM
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I am ignoring all your resistance checks, as I told you they are not valid........

do voltage drop test on, energized circuits.

89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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