: P0621

05-16-09, 09:15 AM
Just got dome changing out my motor mount again and when I fired it up I got P0621 - Generator L-Terminal Circuit.
Is the alternator shot? What can I test? The can has 169000 so it would surprise me if it just went.

05-16-09, 06:28 PM
I pulled the alternator (really sucked) and the battery and had them tested at AutoZone both passed. What else could be setting this code? The little red battery light is getting annoying. I'm getting 14.7 to the battery with the car running.

05-21-09, 10:02 AM
Well I have been driving around for 5 days now with code P0621 will no problems. The voltage to the battery is 14.3-14.9 according to the screen on the dash. Does anyone have any Idea what’s causing the P0621?

05-21-09, 10:19 AM
I'm going to move this to the Northstar section where you may get more help.

05-21-09, 08:50 PM
14.3 - 14.9 volts sounds high - my cars are in the 13s when warmed up

05-21-09, 09:34 PM
Both my '03 and my daughters '02 will run low 15's under full load. DIC info says VOLTAGE NORMAL.

05-22-09, 09:20 AM
Since I bought this car the DIC has said 14.9 volts OK and had code for exceeding 15 volts but I can't remember the exact code off hand. Then one day after recharging the A/C the little red battery light came on.

05-22-09, 09:32 AM
FSM says 14-16V during startup is normal, 13-15V during driving is normal, at idle it may be just outside the range (on the low side ~ 12.5) but will pick right back up to 13+ while driving....

I'd check the connector wire plug on the back of the alternator, if it's got a bad connection or the harness was damaged you have a problem, and the red light on is because the L-terminal is the ground for the warning lamp, i.e. it's failed open because it's not getting a good ground, see here: http://www.autoshop101.com/trainmodules/alternator/alt104.html

Here's a procedure to troubleshoot it: http://www.alternatorparts.com/cs130_sbpage3.htm

You need to get a multimeter on the plug and check for proper grounding, or try to ground the warning lamp connector while it's detached from the alternator. One of 3 things could be causing this, either you damaged the grounding strap usually connects to the upper retaining bolt on the pulley side near battery, or the connector plug on the back with the L-terminal (3 prong plug) is bad, or the connection in the alternator is bad, if it's the first, then you need to get that strap repaired ASAP, otherwise it's more of a nuisance, but it means your indicator for a failing/failed alternator no longer works.

The other thing to consider and realize is that for many of these cars there are 2 different 140AMP alternators, one with a 57mm pulley and one with a 62mm pulley, if you put the wrong one on the car you can end up with different results regarding output voltage...

05-22-09, 09:47 AM
A fully charged "12 volt" car battery reads 12.6 volts, disconnected from anything. A small "battery maintainer" charger floats the battery at 13.2 - 13.4 volts, and a properly operating alternator/regulator supplies from 14.2 to 14.6 volts at decreasing amperage as the battery reaches full charge (the internal resistance goes up and ramps down the charging rate) while the voltage should remain at 14.2 or so.

The Northstar system seems to supply close to 15 volts for a short period after start, but that ramps back to 14.6 or so pretty quickly.

05-22-09, 11:07 AM
I cleaned the connections on the alternator when I had it out but I could of easily knocked loose the other end of the ground wire when I was messing with the belt. I will check it out this weekend.

06-08-09, 08:26 AM
Fixed it. The plug on the back of the alternator had 3 wires on it. I traced them down to where those 3 wires joined a few others (A/C pressure switch, A/C compressor, oil pressure sensor) and right where those wires all got bundled into one the orange wire form the alternator had a nick in it. I pulled on it and it ripped in two. A little solder and heat shrink and the code is fixed!

06-08-09, 03:26 PM
Thanks for reporting back your success