ECU problem?

Output Wire Resistance (Voltage Drop) Test 1. Ensure battery is charged. Turn ignition off. Disconnect negative battery cable. Connect a 0-150 DC ammeter and a voltmeter (0-18 volts) to vehicle's charging system. See Fig. 1 . 2. Connect a carbon pile rheostat between battery terminals. Ensure carbon pile is in OFF position before connecting leads. 3. Connect one end of jumper wire to ground and other end to alternator field terminal Dark Green wire on rear side of alternator. See Fig. 2 . Connect negative battery cable. 4. Start engine. Reduce engine speed to idle. Adjust engine speed and carbon pile to maintain 20- amp current flow. Observe voltmeter reading. Voltage drop should be .5 volt or less. 5. If voltage drop is greater than .5 volt, inspect, clean and tighten all connections between alternator BAT (B+) terminal and positive battery post. If wire resistance (voltage drop) is okay, test is complete. Remove all test equipment.
CAUTION: Alternator has 2 field terminals. In step 3), DO NOT connect jumper wire to alternator field terminal Dark Green/Orange wire. Page 1 of 1 ALTERNATOR - NIPPONDENSO -1993 Jeep Cherokee

Is your check engine light on? If yes turn the key from off to on three times, on the fourth one leave it in the on position, count the flasshes...22 would flash as 2 blinks, then a short puase, then 2 more blinks...if several codes are stored, the pause is longer between codes, code 55 will be the last code...do this and post all codes found...

If the brushes are bad, yes replace the alternator. Charge the battery before you restart it with the new alt.

Take battery and alternator to autozone and have them tested they will put battery under load test to ensure battery does not have bad cell if has bad cell it will not take a charge they will let you know if alternator is putting out a charge and then let us know what the results are

When I was in the Military(VietNam) we had a shop on base for service guy to use, and get help from more knowledgeable guys, Nothing like that on base? Remove the battery cover and see if all cells have water. Do not replace the ECN yet, codes 41 = charging system, alternator, but if the battery has a dead cell, this code will still set. Can also be fusible links, between the alt, and battery.

This is for the 93 Jeep, I will aslo look up the car But I need the model?
TEST CH-2, ALTERNATOR FIELD NOT SWITCHING PROPERLY (CODE 41 ) 1. Put DRB-II in voltmeter mode. Check voltage of Automatic Shutdown (ASD) circuit by probing Dark Green/Orange wire (Dark Green/Black wire on Grand Cherokee and Grand Wagoneer) at back of alternator. If voltage is less than 10 volts, repair open circuit from ignition switch. If voltage is 10 volts or greater. go to next step. 2. Check voltage of alternator field driver circuit by probing Dark Green wire at back of alternator. If voltage is less than 10 volts, go to next step. If voltage is 10 volts or greater, go to step 6). 3. Turn ignition off. Disconnect and inspect PCM connector. Repair, if necessary. Disconnect alternator harness from back of alternator. Using an external ohmmeter, check field driver circuit (Dark Green wire) for resistance. If resistance is less than 5.0 ohms, replace PCM. If resistance is 5.0 ohms or greater, repair open in Dark Green wire. 4. Turn ignition off. Disconnect PCM connector. Disconnect alternator harness from back of alternator. Using an external ohmmeter, check for resistance between alternator field terminals. If resistance is 5.0 ohms or greater, replace alternator. If resistance is less than 5.0 ohms, go to next step. 5. With DRB-II in ohmmeter mode, check resistance in field circuit of alternator harness. If resistance is 5.0 ohms or greater, repair short to ground in field driver circuit (Dark Green wire). If resistance is less than 5.0 ohms, replace PCM. 6. Turn ignition off. Disconnect PCM connector. Disconnect alternator harness from back of alternator. Using an external ohmmeter, check for resistance in field driver circuit alternator harness terminal and cavity No. 20 on PCM connector. See Fig. 4 . If resistance is 5.0 ohms or greater, repair short to ground in field driver circuit (Dark Green wire). If resistance is less than 5.0 ohms, replace PCM. Perform CHARGING VERIFICATION (CH-VER) test. NOTE: Perform TEST CH-1, BATTERY CONDITION CHECK before proceeding.

TEST CH-1, BATTERY CONDITION CHECK 1. If battery has a built-in hydrometer, go to step 2). Turn ignition and all accessories off. Ensure battery voltage is 12.0 volts or greater. If voltage is less than 12.0 volts, charge battery and go to step 3). 2. If battery hydrometer is Green, go to step 3).1f battery hydrometer is Yellow or a bright color, replace battery and perform CHARGING VERIFICATION (CH-VER) test. If battery hydrometer is dark in color, charge battery and go to next step. 3. Ensure battery cables, terminals and posts are clean and tight. Perform a battery load test by applying a 300-amp load for 15 seconds. Wait 15 seconds to allow battery to stabilize. Apply a load equal to 50 percent of battery cold cranking rating for 15 seconds and record minimum voltage reading. 4. See MINIMUM BATTERY VOLTAGE table. If battery is below volt age, replace battery and perform CHARGING VERIFICATION (CH-VER) test. If voltage reading is okay, go to next step. NOTE: Perform PRELIMINARY CHECKS under TROUBLE SHOOTING before proceeding. If battery shows signs of freezing or leakage, battery posts are loose or battery has low electrolyte level, DO NOT test.

I have never heard of one being repaired. Usually just replace and move on.

Check with Autozone. I believe they can, but you'd be better off buying a new one.

Check the wiring harness to the PCM to make sure it is tight and not corroded or damaged in any way.

Let me know what you find.

Could be the PCM also check all the fuses

Welcome to the forum, are there any codes? You should be able to get mil codes by cycling the ignition switch, You turn key till dash lites come on, no further. On--off, on--off, on--off, on, then the mil starts flashing, you count the flashes to get the codes. Your looking for two digit codes.

Your pcm could cause a problem, so could the wiring circuits.