I have a 2000 Jeep Grand Cherokee 4.0 and am having some issues. It would crank but not hold an idle and threw codes for bad injectors. I replaced the injectors and the code went away but no difference. So I got a new battery (old one was getting bad) and still nothing. I then started to replace the crank position sensor (not bolted down yet but we tested while holding it down). And not much better.

We then pulled the alternator wire and the engine suddenly ran a lot better. I went and got a new alternator and now it will hold a rough idle but the lights will dim and the dash will go out when you open the throttle body. We checked the battery while running and it was getting 17 volts. They were saying to find out where the voltage regulator is but I thought it was in the alternator.

Any help on this would be great. I will be getting a new bolt for the CPS and finish putting that in Saturday in case it not being seated right has some sort of issue.

 

The voltage is controlled by the PCM. Underneath the battery, there is a temperature sensor that tells the PCM to cut back the charge rate when the battery gets hot. I would suspect that sensor is defective or disconnected. It is a thermistor (temperature variable resistor) and can be checked with an ohmmeter. It should read about 12,000 ohms at 70*F, lower with higher temps.