Check engine light coming on

[RLDaily]

Right now I have P0157 H C and I think it's giving me a check engine light, what's the deal?

I haven't done any mods, everything seems to be OK and the light goes out when I reset everything but it's come on 3 times now.

Do I replace the sensor or what?

What could happen?

 

[timfitz63]

Sounds like you've got an intermittent (and persistent) problem with an O[SUB]2[/SUB] sensor; the P0157 code (according to this site) decodes as "Heated Oxygen Sensor (HO2S) Circuit Low Voltage Bank 2 Sensor 2." The "H" and "C" indicators after the code tell you that it's both an historic (old) and current code. You might peruse this 'sticky' at the top of this sub-forum to get more details on reading and interpreting codes.

I'm speculating that perhaps a wire or connector on the sensor is making intermittent contact?

 

[RLDaily]

Could be, heavy winter an ice driving might have done something...Is this the right rear sensor (passenger)?

 

[Hib Halverson]

That's a fault in the sensor heater circuit for the rear O2 sensor on the passenger side. The fault is low voltage. That could be cause by one of several issues such as high resistance in the heater circuit, bad ground in the heater circuit, faulty sensor or faulty ECM and there might be other causes, too.

As "timfritz63" suggests, the fault was present when you read the codes (the "C") and it's been present in the past (the "H").

If you keep clearing codes and it keeps coming back further clearing of codes or wishing on a star :L will not help. You need to diagnose the heater circuit then fix the cause.

If you want to repair that DIY, my suggestion is to read the Factory Service Manual info for that DTC, follow the diagnostic instructions then repair wiring, repair connectors or replace components as called for by the info in the FSM.

 

[RLDaily]

Any potential damage because of the sensor problem?

 

[dadaroo]

Any potential damage because of the sensor problem?

No, just an emissions issue.

 

[timfitz63]

No, just an emissions issue.

I think it could affect gas mileage too, but don't quote me on that...

 

[Hib Halverson]

No, just an emissions issue.

Well....there's more than just that.

If you register the car in State which requires emissions testing, the car will flunk, instantly if you go to test with the light on.

Also, when the MIL is on, the PCM may use low octane spark tables and some other features of the calibration which may prevent the engine from performing its best and getting the best fuel mileage it can.

The main role of the rear sensor on each side is to provide the data for the catlylist monitoring required by OBD2 emissions controls systems.

 

[RLDaily]

I appreciate it Hib but if you'd notice I'm in Arkansas where a great deal of Federal law isn't recognized and the state legislature would get tarred and feathered to even mention CARB air standards (I was an environmental manager for a major aircraft corporation activity under South Coast Air Quality regulations for quite a while)

Right now I drove about 350miles over the last 2 days and averaged about 26mpg on Ark State hiways with an average speed of about 40mph (that's counting stops and all that along roads posted 55mph and through small towns).

I'm finally getting a break and I'm going to spend the weekend doing some troubleshooting as well as some planned maintenance on the ride (I'm a licensed A&P with specialization in turbine/helicopters so the car isn't that difficult).

I've gotten so good info that I'm going to use, so folks thanks, and as the Terminator said "I'll be back"

 

[dadaroo]

Well....there's more than just that.

If you register the car in State which requires emissions testing, the car will flunk, instantly if you go to test with the light on.

Also, when the MIL is on, the PCM may use low octane spark tables and some other features of the calibration which may prevent the engine from performing its best and getting the best fuel mileage it can.

The main role of the rear sensor on each side is to provide the data for the catlylist monitoring required by OBD2 emissions controls systems.

Yes I know, but he asked a specific question which was is it causing damage.

 

[Hib Halverson]

Yes I know, but he asked a specific question which was is it causing damage.

I don't want to get bogged down in arguing over the meaning of the word "damage", but as I see it, if driving with the rear sensors not working and the MIL on, decreases performance of the engine, my enjoyment of it is "damaged".

Now in a literal sense, can the engine or the engine controls be damaged if catalyst monitoring is not working and he MIL is on for an extended period? It's possible, but unlikely, I'd say, but...I'm not 100% sure.

You seem to be more confident than I, "dadaroo" so please share with us the greater knowledge of or experience with engine controls systems you have that makes you confident there will be no damage to that engine if it is run for an extended period with the MIL on and cat monitoring inoperative.

 

[dadaroo]

Sorry, did not factor in emotional damage. Mr. Sam, P.E.