Conditional low charging problem

UOY3MTA3

MEMBER
1998 PONTIAC FIREBIRD
5.3L
V8
TURBO
2WD
AUTOMATIC
290,000 MILES

I have replaced the alternator, battery (posts included), belt, and tension pulley because I had a charging problem. I also cleaned all of the connections in order to ensure there was no discontinuity. Two months earlier I replaced the starter motor because it seized. None of that was a problem because it still exists. But this is now out of my understanding and here is why. This might be easier if you pound a six pack before trying to guess this one.

I know I can trust the gauge inside the vehicle because I have tested using a volt meter.

When I start the car the charging system is perfect, just above 13 volts. And it stays that way until the thermostat opens. That is when things change.

When I stop at a light, I can watch the meter go down to 10 volts, just right above the red zone. If I depress the gas pedal in any gear the charging system will go to 12.6 volts and never any higher. When I start moving, the charging system will stay at 12.6 volts.

Time to hammer down the six pack. Keep in mind I do almost 100% of my driving during daylight hours. Over the past few days I have had to do some night driving. When I flip the head lights on, the charging system stayed above 13 volts whether or not I was moving. The needle never dropped.

When I am coming to a stop I push the gear into neutral. That slows down the process. When I come to a stop I increase the RPM's from 700 to 1000 or 1100. Most of the time that is enough. Recently I have had to go as high as 1,500 RPM's in order to achieve the same results. And that's just holding at 12.6 volts. Even if I run the RPM's up to 3,000, the charging system is still only charging at 12.6 volts. As a result there is no point in forcing a higher RPM than what I can achieve at 1,100 unless the gauge starts to drop when I am at 1,100. (Is the beer helping?)

There is one other thing. When I have the charging issue, the temperature gauge will be at about 200 degrees. When I do not, the temperature is about 165 degrees. I think this is a result of the low voltage because when I have the issue, the AC is not as cold, I will receive an error message P430, which is not valid. I have not received that error since I realized that manually increasing the RPM's helps to minimize problems.

I hope I provided enough information. If you have any clue as to what can be wrong, I would love to know.

Thanks in advance,

Steve

5 Replies

ASEMASTER6371

MECHANIC
52,797 POSTS

Good morning.

The 430 is a valid code for bank 2 catalytic converter. The precious metals are worn out internally and the catalytic converter. needs to be replaced.

The charge rate is way off. It should 14 to 14.5 volts to be charging the battery. The fact it is so low is the reason for your charging issue. Most likely you need to start with another alternator.

Roy

https://www.2carpros.com/articles/how-to-check-a-car-alternator

430

CIRCUIT DESCRIPTION
In order to maintain a reasonably low emissions of Hydrocarbons (HC), Carbon Monoxide (CO), and Oxides of Nitrogen (NOx), the engine controls system uses a three-way catalytic convener. The catalyst within the converter promotes a chemical reaction which oxidizes the HC and CO present in the exhaust gas. This reaction converts them into harmless water vapor and Carbon Dioxide. The catalyst also reduces NOx, converting it to Nitrogen. The PCM monitors this process using Bank 1 HO2S #2. Bank 1 HO2S #2, located in the exhaust stream past the three-way catalytic converter, produces an output signal which indicates the oxygen storage capacity of the catalyst. This determines the catalysts ability to convert exhaust emissions effectively. If the catalyst is functioning correctly, the Bank 1 HO2S #2 signal will be far less active than that produced by Bank 1 HO2S #1. If a problem exists which causes the PCM to detect excessive Bank 1 HO2S #2 activity outside of an acceptable range for an extended period of time, the PCM will set DTC P0420. This indicates that the three-way catalytic converters oxygen storage capacity is below a threshold considered acceptable.

CONDITIONS FOR RUNNING THE DTC
- No AIR, CKP, CMP, IAT, IC, MAF, MAP, ECT, TP, EVAP, Left Bank HO2S, Misfire, Left Bank Fuel Trim, Injector, VSS, Engine Protection, or Transmission DTCs are set.
- The ECT is greater than 65°C (149°F).
- The vehicle speed is between 32 km/h (20 mph) and 136 km/h (85 mph).
- The IAT is greater than -30°C (-22°F).
- The TP sensor angle is greater than 2%.
- The engine speed is between 800 RPM and 3000 RPM.
- The MAP is between 25 kPa and 80 kPa.
- The engine air flow is between 14 g/s and 40 g/s.
- The fuel system is operating in closed loop fuel control.

CONDITIONS FOR SETTING THE DTC
The PCM determines the oxygen storage capability of the catalytic converter has degraded below a calibrated threshold.

ACTION TAKEN WHEN THE DTC SETS
- The PCM illuminates the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.
- The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Freeze Frame and/or the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
- The PCM turns the MIL OFF after three consecutive drive trips that the diagnostic runs and does not fail.
- A last test failed (current DTC) clears when the diagnostic runs and does not fail.
- A History DTC clears after forty consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures.
- The PCM battery voltage is interrupted.
- Use a scan tool in order to clear the MIL/DTC.

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
4. Before replacing the three way catalytic converter, make sure that any conditions which may have caused the catalyst to be damaged have been corrected.

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Monday, July 23rd, 2018 AT 2:16 AM

UOY3MTA3

MEMBER
2 POSTS

Thank you for your reply and your suggestions. I took the old and replaced alternator to a shop and had them both tested. Both of the alternators are just fine. Keep in mind I replaced the alternator, belt, tension-er, and the battery because this problem existed. The battery I replaced simply because it was four years old and not an Optimum battery. My current one is. I know it is not the battery because I can charge it just fine with my charger. I know the belt is fine and the alternator is fine. There is something that controls how the engine will idle at different temperatures. And whatever that is is no longer functioning properly once the engine has reached about 180 degrees. And the other on saying is that when I turn on the lights, this problem goes away. Technically it should make it worse. Replacing the alternator is not going to solve this problem. If you have any other suggestions I welcome them.

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Tuesday, July 24th, 2018 AT 6:35 AM

ASEMASTER6371

MECHANIC
52,797 POSTS

At the back of the alternator, the red/black should have battery voltage.

The red wire is hot with the key on. Verify this wire has power.

Yes, the PCM controls turning the field on and off based on electrical load. It could be the problem but need to be sure all the powers are good.

Roy

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Tuesday, July 24th, 2018 AT 8:02 AM

UOY3MTA3

MEMBER
2 POSTS

I have checked every possible connection there was. Everything checks out okay. What I did not think about was the PCM. And that is probably it. Now that I think about it I have seen the voltmeter drop then go back up and drop again and then stay that way. That sounds like the PCM was trying to take over and failed. It might also explain why everything works better when I turn the lights on. I am requesting even more power. And then something inside of the PCM two sides to provide it.

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Tuesday, July 24th, 2018 AT 8:26 AM

ASEMASTER6371