Honda 2 items can they be related???

[LazyDog]

The vehicle in question is a 2004 Honda CRV w/ close to 190K. Original Alternator and Starter. I been chasing an engine Po134 for quite some time and finally got a scanner that allows me to see what the computer is doing at the point where it triggers it: The computer turns off the ground side control to the heater side.

I also bought one of those volt meters that you plug in cigarette lighter and found some interesting results.

Run 1
1. Clear engine code and start car,
2. RPM's are around 1100 when cold
3. Drive car normally
4. Has the car warms up around 3 miles, rpm's are dropping
5. The moment the check engine lights up, the voltage drops from 14.1 to 12.1
6. Is this a fluke or I got to 2 unrelated problems

Run 2
1. Clear engine code and start car,
2. RPM's are around 1100 when cold
3. Drive car hard, just like you stole it
4. I can maintain the light off for several miles as long as the rpm's are high
5. The moment the check engine lights up, the voltage drops from 14.1 to 12.1
6. Is this a fluke or I got to unrelated problems

 

[JeffKeryk]

Isn't that an oxygen sensor failure?

 

[Cujet]

Hard to know. It could be that the computer controls the voltage, the O2 heater and at the same time, provides diagnostic information. In other words they are all on the same "clock".

 

[LazyDog]

Isn't that an oxygen sensor failure?

I tested the resistance at the sensor and is fine.

 

[LazyDog]

Hard to know. It could be that the computer controls the voltage, the O2 heater and at the same time, provides diagnostic information. In other words they are all on the same "clock".

Interesting idea. Yes, the computer is controlling the heater but I am just curious that the voltage is very low at 12.1.

This drop also occurs at low rpm's which makes me wonder if I need to replace the alternator first. In other words, the computer sees the low voltage and turns of the ground at heater to save the battery. The alternator is original from 2004.

 

[Cujet]

I think the heater is just used for a period of time during warm up.

You might want to measure voltage somewhere more reliable. I'll bet the voltage is not 12.1 at the battery but more likely 12.8. Many vehicles manage voltage by battery state of charge. It used to be that cars would maintain 13.8 or so. But as time went on, manufacturers managed battery health more accurately, and now try not to overcharge the battery.

 

[LazyDog]

I think the heater is just used for a period of time during warm up.

You might want to measure voltage somewhere more reliable. I'll bet the voltage is not 12.1 at the battery but more likely 12.8. Many vehicles manage voltage by battery state of charge. It used to be that cars would maintain 13.8 or so. But as time went on, manufacturers managed battery health more accurately, and now try not to overcharge the battery.

Yes,
This charging system is computer controlled and it has an ELD/ Electrical Load Detector on the fuse.

I might make more changes by turning the AC system on which bring the cooling fans, plus the compressor and probably the defrost to see what it does to the voltage.

Thanks for the replies!

 

[Trav]

Without being able to check it out the alternator sounds like it is working normally. Check the O2 wiring and signal voltage (not the heater) when the engine is in closed loop, you probably have a bad O2.

https://opensiuc.lib.siu.edu/cgi/viewcontent.cgi?article=1011&context=auto_pres

 

[Kira]

Can you turn on "every option" and repeat your tests?
Maybe the initial higher voltage output (needed to power every option) will effect some change you can detect.
How old or healthy is the battery?
I thought something with the regulator too.

 

[wpod]

Clean the battery terminals and check for Voltage drops at the grounds?

 

[meep]

Artificially boost voltage as a test from a charger or with cables to another vehicle?

turn the headlights on? That may command a voltage increase out of efficiency mode?

 

[Marcozi]

It sounds like the alternator is going bad. The voltage should be over 14VDC when the engine is running. The sudden drop in voltage can be the route cause of the code. These cars are rolling computers and whacky voltages cause whacky problems.

 

[JimPghPA]

It sounds like the alternator is going bad. The voltage should be over 14VDC when the engine is running. The sudden drop in voltage can be the route cause of the code. These cars are rolling computers and whacky voltages cause whacky problems.

+1 on that "whacky Voltages cause whacky problems".


An in that line of thinking Hondas are notorious for doing strange things electrically when the battery is going bad. And the 51R is somewhat undersized. Many upgrade to 24F or at least 35N. The forum "Honda CR-V Owners Club Forum" has info what part no's for biger battery tray.

 

[LazyDog]

Just an update, I am hoping that today's findings would get me closer to finding the solution to my P0134 engine code.

Exhaust leak in front of the AFR where the after market cat was welded to the remains of the OEM cat.