P0058 Code on 2004 Dodge Durango

[David Moyle]

Hi folks, I have a 2004 Dodge Durango which started showing the check engine light – the trouble code is P0058, which is apparently a heater coil malfunction on the downstream O2 sensor. Since the car has 160K miles on it I bought a replacement and installed. The car ran about a mile with the engine light off and then it triggered and came back on. I checked the continuity of the heater coil wires and there is continuity. Are there other tests I can perform on it? If the new one has failed, what might cause it? I am led to believe it either gets 12 volts or no volts to turn it on or off.

Thanks

Dave M

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[David Moyle]

Bump

[Andrew Phillips]

P0058 means the control circuit for the O2 heater is ‘high’. Forgive the following background info if you already know it, I just like to post info like this since a wide variety of people with different levels of experience read these posts.

When a circuit is high, that means there is positive voltage where there shouldn’t be, such as a wire than should normally be at 0v (ground) is shorted to positive voltage abnormally. The O2 sensor heater has a constant battery voltage applied (when the key is on) and the engine computer (ECM) switches the heater on and off according to its programming by controlling the heater’s ground. This is called a ground-switched circuit. Since the replacement sensor didn’t solve the problem, consider the following. There are three possible scenarios that would cause the control circuit to report a ‘high’ state when it shouldn’t be.

1) The O2 sensor heater has a faulty coil. The heater coil is shorting voltage to the controlled ground. You did replace the sensor, but don’t forget that parts can come bad right out of the box. Put an ohmmeter on that heater (key off!) and measure its resistance. It should be low, but not zero. Exact values vary by year/make/model and I don’t have the specs handy on yours, but if I were testing it without specs, I’d look for a value around 3-5 ohms, across the heater coil. Japanese brands are usually a bit higher, in the 11-15 ohms range.

2) The control wire is broken (open), or the ECM has a fault. Because this is a ground-switched circuit, the ECM has a pull-up resistor inside to make sure that when the ECM is not commanding the heater on that the driver is pulled up to battery voltage. With the voltage potential present and equal on both sides of the circuit, current cannot flow, so the heater does not operate. To turn the heater on, a transistor in the ECM defeats that resistor by pulling that line low (to ground) and because now that the heater has a voltage potential difference (voltage on one side, ground on the other), current flows, operatesperates. Due to the high current demands of some O2 heaters, it is not unusual to sometimes find that the ECM doesn’t directly control the heater, but instead controls a relay which in turn controls the heater. I do not believe your vehicle has a relay, but I do not have the wiring charts handy for yours at the moment so I cannot say for sure. To test this, you will want to connect a test light clip to battery positive and probe the controlled ground. When the sensor is supposed to be on, key on, and some ECMs need the engine running to turn the heater on, the test light should light up. If it does not, then repeat this test at the ECM itself (you will probably need a wiring diagram to locate the correct position of this control wire, and the wire color should be the same at both ends). If you get the expected ground at the ECM but not at the sensor, then the wire is broken between the ECM and the sensor. Sometimes a wire can be broken inside the insulation but visually the wire looks fine. Also make sure to check any intervening connectors for corrosion and proper pin fitment and tight connection. Testing continuity to ground for this test is not reliable since this heater ground is a controlled ground and does not go directly to the main ground. If evidence of ground cannot be obtained in either location and the wire has continuity along its entire length, then the ECM’s driver circuit for the heater has most likely failed.

3) The control wire is shorted to voltage or the ECM has a fault. The wire for the controlled ground has become damaged somewhere and is shorted to a positive voltage source. If visual inspection yields no evidence of damage, check this wire with a voltmeter for voltage while the key is on as in #2, again with some ECMs needing the engine running for this. If there is no voltage present on the wire, and no evidence of physical damage all the way from the sensor to the ECM causing a short, then there is a fault with the ECM’s driver circuit transistor and the pull-up resistor is pulling the circuit up like it is supposed to, but because of the faulty transistor, there is no output on the control wire. This appears as if the control wire is open, even if it has continuity along its entire length, because the wire is actually fine, the fault is most likely inside the ECM.

[David Moyle]

Thank you!!! This is the best explanation of what is going on that I have read (and I have read a lot of web searches since the original post). I always have trouble getting my head around a ground controlled circuit. I tested both the original and the new sensor – original measured about 6 ohms, replacment about 4 ohms. I also checked both by measuring the voltage output while heating the sensor tip with a torch – both sensors appear to be OK (could have saved myself $60 if I had done this first). Of course the wiring harness side of the sensor clip is nearly impossible to reach, but I did manage to get a test clip on both the powered pin and the grounded pin (if I had to do this over I would have cut the leads to the sensor and used the leads on the sensor side (with the plug left plugged in) to get easy access to the power and ground wires – duhhh) When I tested it, I had the key on but not the car running. I measured 0.7 volts on the power side and no volts on the ground side. Not having read your post at this point, I plugged the sensor back in, Cleared the codes and started the car. No engine light. I took the car for a 5 min ride to make sure it was warmed up and still no engine light. I’m thinking that the plug itself may be the problem – I’ve read these are in a position where water drains on them. I may have either cleared off some corrosion or inadvertently unshorted a wire that was shorting out the control wire. At this point, I am going to just drive the car and see if the problems shows up again down the road. Thanks to you, I now understand how this thing works and what to look for :). I’m very appreciative of the time you took to explain it all. Thanks again!!!

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