Question about 1998 Jeep Cherokee

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Faulty pcm need info on how to install external voltage regulator

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  • genes2000joe Nov 03, 2008

    2002-doge durango. while driving at high speeds engine revs up and down.

  • yadayada
    yadayada May 11, 2010

    external voltage regulator for what system??



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Posted on Oct 10, 2008


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2007 saturn vue hybrid system not charging 2.4

Did you test the electrical circuit's ? Have a scan tool hooked up ? Did you have a qualified repair shop check it out ?
When the engine is running, the generator control signal is sent to the generator from the engine control module (ECM)/powertrain control module (PCM), turning on the regulator. The generator's voltage regulator controls current to the rotor, thereby controlling the output voltage. The rotor current is proportional to the electrical pulse width supplied by the regulator. When the engine is started, the regulator senses generator rotation by detecting AC voltage at the stator through an internal wire. Once the engine is running, the regulator varies the field current by controlling the pulse width. This regulates the generator output voltage for proper battery charging and electrical system operation. The generator F terminal is connected internally to the voltage regulator and externally to the PCM. When the voltage regulator detects a charging system problem, it grounds this circuit to signal the PCM that a problem exists. The PCM monitors the generator field duty cycle signal circuit. The system voltage sense circuit receives B+ voltage that is Hot At All Times through the ECM/TCM fuse in the underhood junction block. This voltage is used by the regulator as the reference for system voltage control.
This vehicle uses Class II and controller area network (CAN) communications. The ECM/PCM are CAN and the body controller systems are Class II. The body control module (BCM) acts as the gateway between the different communication protocols. The ECM/PCM requests the battery lamp on the CAN communication line and then the BCM sends a request to the IPC for lamp illumination.
The ECM/PCM will request the battery lamp on under the following conditions:
• The ECM/PCM interprets the ignition is in the accessory position.
• The ECM/PCM is in the RUN power mode with the engine not running.
• Generator L terminal fault has been detected.
• Generator F terminal fault has been detected.
If the generator is not charging, it pulls the F terminal low causing an F terminal fault. Low voltage threshold is 10.5 volts for 4 minutes and engine at least 1,300 RPM. High threshold is 18 volts for 5 minutes.

Do you know what DTC'S diagnostic trouble codes are ?
DTC B1325
DTC B1327
DTC B1328
DTC P0562
DTC P0563
DTC P0615
DTC P0621
DTC P0622
These are all for the charging system .

Oct 19, 2017 | Saturn Cars & Trucks

2 Answers

Where is the voltege regulator in a 1994 f350 7.3

Jorge, You probably have an alternator on that truck,which means the regulator is built into it. Check the attached links,instruction and guides, Good luck

"I hope this helped you out, if so let me know by pressing the helpful button. Check out some of my other posts if you need more tips and info."

dum b question Where my voltage regulator 1994 F250 IDI with factory turbo...

1994 ford f350 7 3 voltage regulator Google Search

where is the voltage regulator located

May 31, 2016 | Ford F-350 Cars & Trucks

1 Answer

How to make transmission shift after installing external voltage regulator on 2003 Dodge ram2500 van 5.2 liter eng

Well this didn't come an external regulator. It is built into the PCM. So, my first would be check the transmission/EATX fuse. Next remove the regulator and replace the PCM. Not saying you can't do this, I would have to see schematics and which wires were patched into or removed. Could be you spliced into alternator wires that should have been cut( or vice versa) from the PCM. The regulators of yesteryear are not what they are today.

Mar 05, 2016 | Dodge Cars & Trucks

2 Answers

I have 2003 Saturn Ion and I have bought a new

test the battery voltage while the engine is running, (you'll have to jump it again)
if you know the battery, voltage regulator and alternator are good, you may have to check all the fuse-able links on the car, all the vehicle grounds, and the fuses and relays.
if you put your battery on charge until it is fully charged and let the car sit over night and it is dead, either the battery is internally shorted or the vehicle is drawing far to much current and each circuit tested to find the short.

Oct 01, 2014 | 2003 Saturn ION

1 Answer

Have code P1682 on 98 dodge durango. I know it's low voltage detected. I pulled the alternator off and had it tested three times and it shows to be good. Have looked at the wireing and everythi

ck the fuse but this vehicle has a built in voltage regulator in the pcm and you have to either install a different pcm and then have it reflashed for your vehicle or install and external regulator i believe napa sells these as i have replaced quite a few of these in our shop.

Jan 24, 2013 | 1998 Dodge Durango

1 Answer

I have a 93 jeep grand cherokee changed altenator but still wont charge

If no damaged wiring is found, it's most likely an internal fault in the ECM (Engine control module, computer, PCM, ECU, whatever you want to call it, it goes by many names)
The Voltage Regulator is built into the ECM on virtually every Chrysler product (including Jeeps) after 1987 or so. And it is prone to failure. If it does fail, you either have to replace the ECM or install an External Chrysler Voltage Regulator, which requires some wiring harness modifications and a few parts that can be purchased at your favorite auto parts store.
To do the External conversion, you'll need :
1 Chrysler Voltage Regulator (virtually any Dodge/Plymouth from 1970 - 1986. It's best to order one for a 70's 4x4 Truck with a 318 engine though, to avoid any possible mix ups)
1 Chrysler Voltage Regulator Pigtail (this is the plug that connects to the regulator)
Roughly 10 feet of 14 gauge wire, possibly less, depending on where you want to mount the regulator.
Most, if not all Regulators now include a wiring diagram in the box, for this purpose, just follow the diagram and match up the field wires on the alternator with the ones in the diagram. On a '93 Jeep one field wire should be Blue, the other should be Green.

Aug 23, 2011 | Jeep Grand Cherokee Cars & Trucks

2 Answers


You are misunderstanding the manual. There is a voltage regulator and it is part of the engine computer. When the regulator goes bad, you need to replace the computer. Its a really bad design but that's the way it is!!! There is a "work around" involving bypassing the computer and installing an external regulator but it turns the light on and won't pass inspection that way.

May 31, 2011 | 1993 Jeep Grand Cherokee

2 Answers

Looking for altennator fuse on 2003 ford windstar

check fuses 13 and 20 in the box by the battery.

May 25, 2011 | Ford Windstar Cars & Trucks

2 Answers

I need to know how to locate the external regulator for the alternator and where it is

The alternator is reglated by the Powertrain Control Module. (PCM) The PCM is mounted right next to the Power Distribution Center, which is mounted right next to the battery in the engine compartment.

Oct 24, 2009 | 2000 Chrysler Grand Voyager

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