code 45
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From: Lafayette, Indiana
code 45
1990 305 tpi keeps throwing code 45 (O2 rich) 2nd o2 sensor in a year (new one in only a few days) and car has had a solid tune up....yes I reset the codes after putting in the new sensor.....any ideas?
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Gonzo,
Inspect the O² sensor wiring. Make sure none of the wires are burned or grounded, and all connectors are clean and tight.
Do you have any other indications of a rich mixture, like poor mileage, raw fuel in the exhaust, etc.?
Inspect the O² sensor wiring. Make sure none of the wires are burned or grounded, and all connectors are clean and tight.
Do you have any other indications of a rich mixture, like poor mileage, raw fuel in the exhaust, etc.?
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Junior Member
Joined: Sep 2000
Posts: 42
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From: Lafayette, Indiana
Vader,
My gas mileage has dropped down to around 10 mpg...and it feels "sluggish" at mid throttle. Wide open is fine. I suspect it's actually my cts (even though I don't have a code) checked it last night at 70 deg. and it was showing 1350k.....have a new one on the way....do you think I found my trouble? Thanks..
My gas mileage has dropped down to around 10 mpg...and it feels "sluggish" at mid throttle. Wide open is fine. I suspect it's actually my cts (even though I don't have a code) checked it last night at 70 deg. and it was showing 1350k.....have a new one on the way....do you think I found my trouble? Thanks..
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Joined: Jan 2000
Posts: 19,679
Likes: 316
Gonzo,
It looks like you've found at least a part of the problem:
Even though the CTS reading is incorrect, it is still within the acceptable range of operation, so you won't set a DTC. You will pay the price in performance and gas mileage.
You might also want to consider the O² sensor as another sensor that wears and degrades, and will creep up on you in terms of mileage and performance. Since you've also replaced this, you're ahead of the game.
Another consideration is the PCV system, since it is suppoed to provided some air to the intake and will lean the mixture. The ECM fuel trim tables have this calculated into the equation as part of the mixture and a clogged PCV system will tend to create a rich mixture, especially on a speed-density system where intake air flow is presumed, not measured. You don't necessarily need to replace the valve and tubing - just clean it out with spray cleaner and make sure the valve pintle moves freely.
Another thing to check is the TPS sensor. TPS voltage that is too high will tend to set the mixture rich as well. If I am correct, your '90 should still have an adjustable TPS sensor. Even if it isn't, you can still test the sensor for linearity and make sure the idle position voltage is below 1.0VDC. Idle voltage above that level will make it difficult for the ECM to "read" the TPS and scale the input based on the idle position. If your's is adjustable, try to get the setting as close to 0.54VDC as possible.
Just a few other things to do while your new CTS is in transit.
It looks like you've found at least a part of the problem:
Even though the CTS reading is incorrect, it is still within the acceptable range of operation, so you won't set a DTC. You will pay the price in performance and gas mileage.
You might also want to consider the O² sensor as another sensor that wears and degrades, and will creep up on you in terms of mileage and performance. Since you've also replaced this, you're ahead of the game.
Another consideration is the PCV system, since it is suppoed to provided some air to the intake and will lean the mixture. The ECM fuel trim tables have this calculated into the equation as part of the mixture and a clogged PCV system will tend to create a rich mixture, especially on a speed-density system where intake air flow is presumed, not measured. You don't necessarily need to replace the valve and tubing - just clean it out with spray cleaner and make sure the valve pintle moves freely.
Another thing to check is the TPS sensor. TPS voltage that is too high will tend to set the mixture rich as well. If I am correct, your '90 should still have an adjustable TPS sensor. Even if it isn't, you can still test the sensor for linearity and make sure the idle position voltage is below 1.0VDC. Idle voltage above that level will make it difficult for the ECM to "read" the TPS and scale the input based on the idle position. If your's is adjustable, try to get the setting as close to 0.54VDC as possible.
Just a few other things to do while your new CTS is in transit.
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