Automotive Forums  Where Car Enthusiasts Go to Discuss Cars Online

1995 Rodeo Isuzu 2.6 4 cylinder, Manual Transmission, 2 Wheel Drive, 180,000 miles

Had two problems

Battery was not charging, so I replaced the alternator with a remanufactured one from autozone.  This fixed the problem and I confirmed that it was working by starting the motor and measuring the voltage at the battery at 14.5 volts.  At this point I was working on a second problem, which is the engine would bogg down when you accelerate.  So I was re-adjusting the TPS, replaced the MASS AIR FLOW sensor (and cable, because the connector on the old one had become so bad that it needed to be replaced), and at the same time I was charging the battery, that was low due to the alternator being bad.  Once I was done with these tasks I tried to start the engine, but it wouldn’t start.  I started to investigate and found that I wasn’t getting spark to the spark plugs.  I decided to replace the ignition coil, but still no spark.   Upon further investigation I found that I also didn’t have normal voltage readings at the M AP, MAF.  I checked all of my fuses and relays and fusible links and they all appear to be good.  The only other information that I have is the blower, AC, and charge fuse circuits appear to be dead, both with the ignition on and off (not sure if engine needs to be running).  I tried to trace through the schematics, but still no luck.  Could this be the ECM or is there something else that I am missing?  

No power huh?? sounds like you pulled something off when doing all that work.
BTY,,,adjusting a TPS is new to me. Dont you just replace them?  

I checked the 60Amp Fusible link for continuity and it was good.  I just noticed that the check engine light is not coming on when I turn the ignition on.  I believe that indicates I am either not getting power to the ECM or a bad ECM.  I can't remember if the check engine light use to come on, but it definately is not coming on now.  A new light that is coming on when I turn the ignition on is the RrABS light.  

The RrABS light does go off after a few seconds, so that is a none issue. I checked the power to the ECM (Red/Wht) and it is showing 12 volts, so it is getting power. I have a feeling what happened is when I cut the wire on the MASS AIR FLOW it might have shorted out the ECM. According to the schematics the MAF has 3 wires and a braided wire connected to the AIR FLOW SENSOR SHIELD. I reconnected all of the wires and the braided wire. The thing that I don't understand is the braided wire ends near the connected end and doesn't appear to connect to the MAF. I do see this same braided wire connecting into the ECM.  

Check your splices on the MAF, and change the ECM. Believe it or not I have heard of people changing headlight blulbs and shorting out the ECM. Or changing starters and not disconecting the cables and sparking the starter against the body or block and blowing the ECM, Have seen cars come here with blown ECMs just by "jumping " a drained battery. Any time you are changing ANY eletronic operated sensor , bulb, any part that is electronis, even fuses, DISCONNECT the battery! And wait until the ECM is "brain dead" Usaly 10 to 15 minutes.  A short time to wait to not have to buy a ECM. Even a small "spike" sent through the car can distroy the ECM.  

I replaced the ECM and now everything is working great again.  I would like to thank everyone for their responses.  Took a look at the old ECM and found a resistor was burned out.  

The burnt resistor happened when you cut the wires to the MAF. always disconnect the battery when working on a sensor or any electronic component the feeds to the ECM.