ok, over the last few days I've had a few eletrical problems. My passanger side headlight wouldn't flip up, and my stereo was acting a bit odd (one of the amps wasn't powerd up). well, I wiggled some wires and things, both the headlight and stereo work fine now. So obviously I have a bad connection somewhere and I need to find it.

But this morning my service engine soon light came on when I downshifted to 3rd from 6th going about 73. (427 roush stang, and it wouldn't even race. good think because I would hate to downshift and then have to not race because of the light). Could this have something to do with the loose wires? If I need to park it and not drive it let me know. The engine has no knock, ticks, and is running fine. Idols fine, I can't seem to find anything wrong.

 

You need to get is scanned for any DTC's. Go to Autozone. They do it for free.

As of right now it could be many things.

 

alright. The codes are p0137 (circuit low voltage bank 1 sensor 2)
and p0157 (circuit low voltage bank 2 sensor 2)

So...I'm lost. What do you guys think? Seems like a bad connection to the battery could cause all of these problems? I'll let the people who know better to tell me. I really hope it's not a bad 02 sensor...

 

DTC P0137 HO2S Circuit Low Voltage Bank 1 Sensor 2




Circuit Description
The powertrain control module (PCM) supplies a voltage of about 450 mV between the HO2S high and low signal circuits. The oxygen sensor varies the voltage over a range from about 1,000 mV when the exhaust is rich, down through about 10 mV when the exhaust is lean.

The PCM monitors and stores the heated oxygen sensor (HO2S) voltage information. The PCM evaluates the HO2S voltage samples in order to determine the amount of time the HO2S voltage was out of range. The PCM compares the stored HO2S voltage samples taken within each sample period and determines if majority of the samples are out of the operating range.

The PCM monitors the HO2S voltage for being fixed below a predetermined voltage. If the PCM detects the voltage is below a predetermined voltage, this DTC sets.

Conditions for Running the DTC
Criteria 1
DTCs P0101, P0102, P0103, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0200, P0335, P0336, P0351-P0358, P1258 not set.
The ignition voltage is more than 9.0 volts.
The fuel system is operating in Closed Loop.
The AIR, EGR, and the Catalyst diagnostics are not active.
The fuel trim learn is enabled.
The theottle position (TP) sensor angle is between 2-70 percent.
OR

Criteria 2
DTCs P0101, P0102, P0103, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0200, P0335, P0336, P0351-P0358, P1258 not set.
The ignition voltage is more than 9.0 volts.
The AIR, EGR, and the Catalyst diagnostics are not active.
The Power Enrichment mode is enabled for more than 1.0 second.
Conditions for Setting the DTC
Criteria 1
The HO2S signal voltage remains below 80 mV.
The Criteria 1 conditions are present for 80 seconds.
OR

Criteria 2
The HO2S signal voltage remains below 420 mV.
The Criteria 2 conditions are present for 10 seconds during the Power Enrichment mode.
Action Taken When the DTC Sets
The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure Records.
Conditions for Clearing the MIL/DTC
The PCM turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A last test failed, or current DTC, clears when the diagnostic runs and does not fail.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Use a scan tool in order to clear the MIL and the DTC.
Diagnostic Aids

Important
Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing/replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent contaminant intrusion into the PCM.
For any test that requires probing the PCM or component harness connectors, use the J 35616-A connector test adapter kit. Using this kit prevents any damage to the harness connector terminals. Refer to Using Connector Test Adapters in Wiring Systems.

The PCM sets this DTC when the vehicle runs out of fuel.

Heated oxygen sensor (HO2S) wire--Sensor pigtail may be in contact with the exhaust manifold or the exhaust system.
An oxygen supply inside the HO2S is necessary for proper operation. The HO2S wires provides the supply of oxygen. Inspect the HO2S wires and connections for breaks or contamination. Refer to Heated Oxygen Sensor (HO2S) Wiring Repairs in Wiring Systems.
Inspect for an intermittent ground in the signal wire between the connector and the sensor.
Lean injectors: Perform the Injector Balance Test. Refer to Fuel Injector Balance Test with Tech 2 or Fuel Injector Balance Test with Special Tool .
Fuel contamination: Water near the in-tank fuel pump inlet can be delivered to the injectors. Refer to Temperature vs Resistance . The water causes a lean exhaust and can set a DTC.
Fuel pressure--System will be lean if fuel pressure is low. Refer to Fuel System Diagnosis .
Exhaust leaks: An exhaust leak near the HO2S can cause a lean condition. Refer to Exhaust Leakage in Engine Exhaust.
Vacuum or crankcase leaks can cause a lean condition.

If the above are OK, the HO2S may be at fault.

 

I know that is a lot and its hard to read, but it really lets you know what is going on.

I would get under there and take a look at the o2 sensor wiring. If it looks good and isn't all burnt up or anything, it is probably your o2 sensors.

 

thank you very much. I'll try to make as much sense out of this as I can . But I really appreciate it!

 

well it happened on a downshift, could I have just went lean for a bit?

 

Your welcome.

Its hard to say. Have you done any recent mods like headers or an intake?

 

not recently, but the person I bought the car from did lid/exhaust without tune. Not sure if that would cause it...I"ll just check it out when I get time. Thank you very much for the help

 

Anytime man.

 

Since you have two DTCs(P0137 and P0157) that went SET simultaneously you have to look at something that they have in common since they are related rather than troubleshooting the DTCs individually. If the voltage is staying low(lean) on both banks you need to find out why. I'd put the scan tool(AutoTap or Ease) on it and view the STFTs and LTFTs on both banks. See if they are in range or out of spec. Watch your Bank 1 Sensor 1 and Bank 2 Sensor 1 activity. Are they switching? If not work backwards. Do you have your reference voltage at the O2 sensors? You can backprobe them using a DVOM to find out. If not, start checking fuses. If a fuse is blown just replacing it probably won't solve the problem because it will just blow again. You need to see if a wiring harness is touching ground or if you have a overload(unlikely) since shorts to ground and overloads are the only things that blow fuses.