2001 MDX recurring OBD code P0135

[pvcMDX]

I threw an OBD code P0135 (O2 Sensor Heater Circuit) on my 2001 Acura MDX.

I replaced the Pre-Cat/Upstream Oxygen Sensor with this one from EBay:
GLOBAL AUTOMOTIVE O2 OXYGEN SENSOR ACURA HONDA VEHICLES GA24346

Cleared the P0135 code with a code reader. Drove around the block and threw another OBD code P0135.

I replaced the other After-Cat/Downstream Oxygen Sensor with this one from EBay:
SMP SG342 OXYGEN SENSOR FOR HONDA PILOT

Cleared the P0135 code with a code reader. Drove around the block and threw another OBD code P0135.

Any ideas?

[pvcMDX]

I tested the Pre-Cat/Upstream Oxygen Sensor heater element for Ohms resistance (two white wires). It measured 13.9 so I believe this reading indicates that the sensor heater is okay.

I tested the other After-Cat/Downstream Oxygen Sensor for Ohms resistance (two white wires). It measured 14.4.

If both of the new heaters that I installed are good, then why the heck am I throwing this P0135 (O2 Sensor Heater Circuit) Code?

[pvcMDX]

Oh, one more thing I noticed. With a cold engine I have to drive a block or two before I throw the P0135 code. Though, with a warm engine it will throw the P0135 code quicker after driving only about 20 or 30 feet.

[pvcMDX]

So now I'm stuck between a rock-and-a-hardplace! My OBD problem code P0135 continues.

Do I take it to the dealer and give them a boatload of $$money$$ ?

Do I replace one or both of the O2 Sensors again? If so, are expensive O2 sensors more likely to fix this problem as opposed the inexpensive O2 sensor that I used?

Does anyone have any good or bad experiences with the inexpensive O2 sensors from EBay?

Does anyone know the ohms of resistance range for the 2001 MDX O2 sensor heater?

[phins2rt]

Are there only two O2 sensors on the 01?

[pvcMDX]

Originally Posted by phins2rt

Are there only two O2 sensors on the 01?

Yes, there are only 2 O2 sensors on the 2001 MDX.

Drat!! I thought someone had posted some helpful information.

[phins2rt]

Maybe some info here, if you haven't seen this yet:

http://www.mdxers.org/forums/73-2001...locations.html

[TexasHonda]

I had a similar problem w/ distributor sensor in 1994 Accord. Sensor measured (resistance) fine, but code returned immediately. I measured sensor resistance at the ECU/Harness connector. Same result. This indicated sensor and harness were fine, but ECU had an internal fault. New ECU fixed problem.

I would suggest checking sensor resistance at ECU/Harness connector. If same result, you need a replacement ECM.

good luck

[pvcMDX]

Originally Posted by phins2rt

Maybe some info here, if you haven't seen this yet:

http://www.mdxers.org/forums/73-2001...locations.html

Yes, I read that. "P0135 means it's the rear sensor". "No, P0135 means it's the front sensor". No new information there.

[pvcMDX]

Originally Posted by TexasHonda

I had a similar problem w/ distributor sensor in 1994 Accord. Sensor measured (resistance) fine, but code returned immediately. I measured sensor resistance at the ECU/Harness connector. Same result. This indicated sensor and harness were fine, but ECU had an internal fault. New ECU fixed problem.

I would suggest checking sensor resistance at ECU/Harness connector. If same result, you need a replacement ECM.

good luck

Hmmmm, I'm not sure how to do this? Key on, Key off, engine started but before sensor has heated?? I am hesitant to apply voltage when the ECU unit is involved? I believe applying voltage to the circuit is what I am doing when I measure ohms of resistance, so I am hesitant to try this.

[pvcMDX]

I have ordered and received a new O2 front oxygen sensor. It seems cheaper to buy a new sensor as opposed to taking this to the dealer. I will replace the O2 front oxygen sensor (again) with a new (different brand) sensor to see if this makes a difference. I will let you know in the near future if this was a foolish move.

[hondacuraplanet]

There should be 10-40 ohms between pins 3 and 4. If there is, check for continuity between body ground and HO2S 4P connector terminals No. 3 and No. 4 individually. If you don't have continuity, the sensor is bad.

If there is, at the wire harness side, measure voltage between HO2S 4P connector terminals No. 3 and No. 4. If there is none, then we need to diagnose the connector at the PCM.

If there is, at the wire harness side, measure voltage between HO2S 4P connector terminal No. 4 and body ground. If there isn't voltage, the manual states "Repair open in the wire between the primary HO2S (Sensor 1) (secondary HO2S (Sensor 2))* and the No. 6 FI ECU (PCM) CRUISE CONTROL fuse."

Hope that helps some

[pvcMDX]

Problem solved! Thanks for your replies.

We were barking up the wrong tree about a faulty ECU. Replacing the O2 front oxygen sensor (again) with a new (different brand) sensor has fixed the problem. The P0135 OBD code is gone and stays gone.

This is the first O2 front oxygen sensor that I used with bad results.
NEW GLOBAL AUTOMOTIVE O2 OXYGEN SENSOR GA24346 paid $22.50, now reduced to $17.75.
I tested this sensor heater element for Ohms resistance (two white wires). It measured 13.9

This is the second O2 front oxygen sensor that I used with good results.
Standard Motor Products SG1848 Oxygen Sensor, paid $28.80 now increased to $36.00.
I tested this sensor heater element for Ohms resistance (two white wires). It measured 7.5

Moral of this story for me: Be careful about using the EBay sort tab of Price+Shipping: Lowest first

[pvcMDX]

Originally Posted by pvcMDX

This is the first O2 front oxygen sensor that I used with bad results.
NEW GLOBAL AUTOMOTIVE O2 OXYGEN SENSOR GA24346 paid $22.50, now reduced to $17.75.

This is the second O2 front oxygen sensor that I used with good results.
Standard Motor Products SG1848 Oxygen Sensor, paid $28.80 now increased to $36.00.

The second O2 front oxygen sensor is not working well after all. After a few trips I threw a different OBD code (P0132 High Voltage). Sheesh!

So I bought a third sensor, this one (DENSO 234-4728 Oxygen Sensor) paid $60. The P0135 and the P0132 codes are both gone. I have made several trips and many miles. So I think the Denso has fixed my problems.

After this experience I will stay away from the less expensive EBay sensors and go with brands recommended by my local parts stores (brands like Denso, Delphi, Bosch).