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Hey all,
Vehicle : 2008 Hyundai Tiburon GS 2.0L
Issue : Upstream O2 stopped working.
CEL : P0032, P0132, P0171
Description : Front upstream O2 sensor Pin 3 (O2 Heater Ground) is getting 4.465v with Key in on position engine Off Specification is 0v
Trouble Shooting Steps : “Note not in this order”
1. Replaced all fuses (Interior and Exterior fuse boxes)
2. Tested 3 other ECUs
3. Inspected and cleaned all engine bay grounds
4. checked continuity on the Heater control wire (White w/ Black stripe) pin 3 of O2 connector to pin 59
** Not open
5. Tested Voltage from Connector Pin 3 to chasis ground as mentioned
** Reading 4.465v when specification is 0v
6. Traced the pin 3 wire from the O2 connector to the ECU no damage. All interior fuses were rather corroded looking.
7. Removed and inspected interior fuse panel. Nothing looked particularly bad with the exception of what may be a ABS relay??
*** Relay 5-pin OMRON 95225-3B500
*** This relay has what looks to be heat soak (blue and purple/red discoloring) on 3/5 pins. Pins 30, 87b, 87aSorry for the long post but I am at a loss as to what to search for next. I cant afford to take it anyplace as of right now do to layoff at work. Any and all advice or knowledge would be most appreciated.
Best regards,
Josh
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Replies
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check that the heater circuit has 12v going to it. If so replace the sensor with OE.
If not wiring issue.Thanks,
I knew I forgot something. I have also bought 3 different O2 sensors. I have tested each as well and they are good. It is getting anywhere between 11.97v and 12.3v to the heater based on several times of checking this. I know it is an electrical issue. Based on the factory diagnostic procedures I am getting a short to battery on the ground. Hyundai has the positive to all engine sensors wired together with a joint connector and uses the grounds from the sensors to read the values.
Okay so new diagnostics to add.
1. Oil temp sensor shows a short across both pins, Looks to output 5v for the sensor itself. <- possibly the issue
2. Pin 4(blue wire ECU pin # 59 ) of the O2 connector shows short to Pin 2 (Green, Ecu Pin # 52) on the oil temp sensor.
3. CVVT control valve has 3.4v on the ground pinMy thoughts are scrambled here but it looks to me that somehow the oil temp sensor has a short and the excess Voltage runoff is going to the closest ground.
The oil temp sensor should not be on the o2 heater circuit. You have 12v to the
o2 heater Loss of power?I am still tracing issue, All engine sensors (Sensor Signal wires) run to a single joint connector in the Tiburon. Each sensors ground wire goes to a individual pin on the ECU “This is all based on the Schematics”.
Is the O2 sensor ground a direct connect back to battery ground or is it a switched (open collector) switched ground?
Could you post a schematic here?
Hey, the heater control circuit grounds the the ECU so I believe it is PWM controlled but not 100%. I have been trying to pull the schematic, for 3 days now, that is visually usable. The schematic I am looking at is off of a pay technician site. I am having problem grabbing it in any other form then HTML.
I think you might have a resistive connection on the o2 sensor ground terminal back to the ECU that switches it to ground. It doesn’t take much resistance to cause that 4V reading you are seeing and this resistance might be low enough for you to believe that the wiring is good. Another possibility is that the ECU doesn’t have a perfect path to ground which could cause the same reading you are seeing.
I suggest measuring O2 sensor ground right at the ECU while the sensor is on and also measure edu ground when the sensor is on as well. Put your DMM ground right on battery negative terminal when you are doing this.
When you state resistive connection, do you mean that there may be dirt grime or so and so hindering the connection at the ECU? And as for the path to ground I have been wondering if I have some sort of floating ground somewhere causing the issue. Apperantly the car has a circuit protection Diode somewhere behind the HVAC and the inner firewall. I was starting to lean toward this as the culprit, and thats mainly because it is supposed to be on the ground to the ECU? At least this is what the Hyundai tech lead me to believe.
The most likely cause for a resistive connection will be corrosion. If you have a floating ground, you should be able to see that as a voltage higher than ground on your DMM on what is supposed to be ground (0V). If you put your negative lead of the DMM on battery neg post than, with the positive DMM lead start measuring at the ground terminal of the 02 sensor- work your way back to the negative battery post. When the voltage suddenly jumps from >4V to 0V, you have found your resistance.
For example, measure o2 sensor ground at the sensor, then measure it right at the ECU, then measure ECU ground, then at each connection point leading back to the battery neg post.
I doubt the reverse protection diode is at the ground of the ECU, if that was the case the sensor ground voltage could never reach 0V per spec.
Well I have been chasing ghosts for a better part of a week and a half now. I have replaced 4 main chassis grounds with new terminals and checking for corrosion in the wire. I have probed so many Sensors and pins I am having nightmare that they are strangling me (in reality not the wires just crazy fiance’). My DMM shows grounds on 2 sensors with B+ voltage of almost 5v and every other one reads between 46 and 330 mA. I did find something interesting in that my coil packs (2x) when unplugged have erratic voltages off the ground pins. Do coil packs hold charge like a capacitor or something?
Also My positive battery terminal wire is extremely hot so there is some resistance going on here somewhere.
Heat indicates power which is calculated as the square of the current times resistance. So you either have a lot of current going on or high resistance.
As for troubleshooting electrical issues, when you have a lot of various symptoms or components failing, It most often is easier to pick one failing part and find out why that one fails and ignore everything else for the moment. This will usually lead to an explanation of all your other symptoms anyways, Did you probe the o2 heater grounds as I suggested yet?
Electrical troubleshooting takes a little time to get comfortable, but it is not out of reach for most.
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