svtsnake03

It's a 98 grand cherokee 4.0l. Driving home truck shut off on me, cranks but no start. The cluster doesn't move ( gas, temp and voltage gauge not moving) and no spark from coil. Also the truck can't be read with a scanner now. don't see it being the crank sensor or ignition system due to the cluster issue. I'm guessing the ecu since it won't read or sending the signal to coil. Any advice would be helpful. Also read somewhere that the 02 sensor is the ground circuit for the ecu. The sensor wires did get cut and melted on the cat when the clip broke about a month ago. But i don't see how that would cause that. Truck would run with it unplugged when I had it disconnect before. If anyone has any input I'd greatly appreciate it.

CrazyMacaw

Checked all related fuses both inside and out under the hood?
Checked for other damaged wiring under the hood/chassis?
Checked the ASD relay?
Have you tested the ignition switch itself to make sure it's passing voltage in the "ON" position?
Have you tried wiggling the connectors at the ECU or giving the ECU a tap or two?

svtsnake03

Yes have checked everything. Someone had the same issue as me and said they replaced the ecu and it was the same. Then replace crank sensor and that did it. Weird how that would affect the cluster tho.

czettlera

Hi first of all a maybe stupid question: only the gauges are dead, or the check engine and the check gauge lights also? Anyhow I would measure the voltage supply and the grounds directly on the connector of the ECU (if you need I can send you the pin list). The ECU has separate grounding, it's not supplied by the O2 sensor. In my opinion it doesn't seem likely that one failed sensor could cause all the trouble, it's more like the ECU itself. Is the mileage display working? Have you tried to get failure codes with the key trick?

svtsnake03

If you could send it that would be great. The gauges are dead the engine light is not on (it was before it went dead). The fuel light is on even tho tank is 3/4 full. Mileage shows up. The o2 sensor wire came out of the clip and melted the wires.

Will not connect to read the codes. Whats the key trick?

czettlera

Attached you can find the pin list, and the description for the failure code key trick. The power supply should be present on pin A22, the ground on A31 and A32

czettlera

czettlera

czettlera

I hope it'll help

svtsnake03

Thanks for the information i greatly apprecate it. The key trick did not work for me, ill bring my meter home tomorrow and check all the wires to the ecu. Is there any site that sells ecu's that you guys recomend? Im 95% sure its gonna be the ecu

czettlera

I have only found on Ebay. If you find some good place, please inform me, because I also need a new or a used PCM. In mine the transmission control output is dead.

svtsnake03

Ok we'll I checked for power and ground at the ecu. A7 showed 5.1v at the pcm connector. But at the connector for coil it was showing ground. Then checking it again at PCM got nothing at connector and ground at coil. So it's not getting power and there might be a short. Now I got power to the o2 sensor connector but no ground. The sensor is unplugged. The wiring diagram shows that sensor sharing a ground with the PCM. Any possibility that there needs to be a sensor connected to complete the circuit?

czettlera

I don't think that the o2 sensor is needed for the pcm to start up. Do you have the 13V on the connector A22 pin, measured against the A31 and A32?

svtsnake03

Yes i do but no power from a7. I ordered a pcm

czettlera

I hope it will do the trick. Have you ordered it preprogrammed? I'm also looking dealers, but I'm a little bit afraid of the quality of re manufacturing. I'm to far to send it back if it fails, even in warranty.