2003 Toyota Corolla Electrical issue

Hi I have 2003 Toyota corolla. Recently one of the relay from the fuse box under the steering wheel started making clicking noise. I got it fixed from my mechanic by replacing it twice. When my mechanic checked for codes, he found that there was some problem with igniter circuit and car’s motor is not able to generate enough power. I have observed that whenever I try turning on the heater, the relay also starts making clicking noise. I got it diagnosed from a professional auto electrician but he was also not able to find the fault and now the check engine is on all the time and flashes some time. I don’t know how to fix my car. Need your help.

If the battery voltage is on the low side, this can result. That can affect the igniter too. Has your shop measured the battery voltage while the engine is idling? What’s that measurement? It should be around 14 to 15 volts. Has the battery been load tested?

Yes the battery level was about 13.6v when he checked. The car runs absolutely fine.

13.6 v is a little on the low side if the engine was running. Was it running at the time of the measurement? That could be ok if the battery was already fully charged. W/my Corolla that measurement reads 15 volts when I first start the car in the AM, then goes down to around 14.5 volts after idling in the driveway for 10 minutes.

“car’s motor is not able to generate enough power” and “The car runs absolutely fine.”

I’m a little confused here. But in the meantime, go to a mechanic or a parts store that will read codes for free and get the codes read. Post the actual code here, not what someone says the code means.

So should I get battery check again or should straight away go ahead and buy a new battery

@keith what could be possible reasons for a car to not generate enough power in this case

When my mechanic checked for codes, he found that there was some problem with igniter circuit and car's motor is not able to generate enough power.

So you can definitely feel a lack of power while driving?

Yeah a lil bit. I always give my car a slow pick up and not pressing the throttle completely

Get the codes read, as Kieth said above. Done free at Autozone, Advance Auto, O’Reilly’s, and others.

It would be good to have the charging system checked out to make sure it is working okay though it seems like it is from what you say about the voltage. The 13.6 volts is on the low side of good for a charging voltage and you really didn’t say what the conditions were when the voltage reading was taken. If there were systems turned on and the engine was just idling then that voltage level is really good.

It seems from what you stated that the voltage for the ignition system may be low. That could be due to either a bad engine ground connection or a bad power connection after the fuse panel. I would verify that the ignition voltage level is okay at the fuse in the dash fuse panel and then at the ignition. It would also be good to clean the ground connections under the hood. That is a fairly common issue when having engine operation trouble. Just cleaning the ground connections under the hood may solve the problem.

The ground could be dirty or the 12 volt connection could be dirty. The alternator could be bad. Battery cables could be bad or dirty.

An alternator usually contains three separate charging coils, each using 2 diodes. If a single diode fails in one coil, the alternator may still work but will produce too low of a voltage and won’t be able to fully charge the battery and/or run the car’s electrical systems properly. Such as the igniter, which uses quite a bit of current. At a minimum OP should have the battery load tested and the charging system tested. That’s a standard procedure that any shop can do. Some auto parts store will do that for free if you ask.

A flashing check engine light usually indicates a misfire, get the fault codes from the computer.

Your charging system voltage is normal, tell us which relay is clicking so that we understand which circuit is malfunctioning.

Here’s a web link about typical charging voltage


@GeorgeSanJose That information is outdated. Target charging voltage is normally based on ambient/battery temperature. A charging system voltage of 14.5 volts will only occur in cold weather. In my area 13.2 to 13.8 is normal charging system voltage, the hotter the temperature the lower the target voltage to prevent damage to the battery.

Thanks for the update @Nevada_545 . Just curious about when all this changed in auto electrical design? My 20+ year old Corolla, I measured the voltage at the battery a couple of weeks ago as part of my winter prep routine. On the first start of the day – temp was about 60 deg F – it initially measured 14.9 volts. After idling for a few minutes it dropped to 14.4 volts. Only after driving for some time, like driving it on the freeway for 15 minutes, does it drop to 13.6.

Toyotas of this time period adjust the charging system voltage based on the voltage regulator temperature, others use the PCM and temperature sensors.

This is from the service manual for 2003;
(No load test)
© Check the charging circuit (DENSO made).
(1) With the engine running from idle to 2,000 rpm,
check the reading on the ammeter and voltmeter.
Standard amperage: 10 A or less
Standard voltage: 12.9 − 14.9 V

It doesn’t define thee correlation between temperature and voltage but as you can see with your car when the engine compartment is at full operating temperature the voltage is reduced.

This is from the 1992 service manual;

(b) Check the charging circuit as follows:
With the engine running from idling to 2,000 rpm,
check the reading on the ammeter and voltmeter.
Standard amperage: Less than 10 A
Standard voltage: 13.9 − 15.1 V at 25C (77F)
13.5 − 14.3 V at 115C (239F )

Thanks for taking time to look it up, that explains why w/ newer cars you might see a lower charging voltage compared to what you see on older cars.

I went to my mechanic and he found that the alternator was not charging the battery when AC, music system and headlight on while the voltage remains at idle at 13.6v with engine running and all other system are off. So my mechanic replaced the alternator.

The code in the computer where

  1. P0300 Random /multiple cylinder misfire
    2)P1300 Igniter circuit fault #1
    3)P1305 Igniter circuit fault #2
    4)P1310 Igniter circuit fault #3

The most strange part is that after fixing alternator, the car’s check engine light again came up and showed me the same codes again.