robkee4

I'm sure the is a thread somewhere but I can't seem to find the exact answer. I started my 2000 Cherokee 4.0L the other day, it ran rough then stalled after 5-10 seconds. I tried to start it again and it gave me the "no bus" reading on the odometer. I tried hitting the dash, changed the crankshaft position sensor, check all fuses, then tried starting it with starter fluid and nothing so I have no spark either. Also when I turn the key I do not hear the fuel pump turn on. Any ideas on the next thing to check would be? Also can anyone supply me with a list of the sensors that affect the "bus" so I can check each one.

Rockfrog

No bus is a communication error between the PCM and the dash.
Check the grounds point on the driver side fender, pull, clean and reattach. Might help, but if the engine won't run it may be a deeper issue. If you haven't already, pull the cluster and clean the contacts (careful not to bend the pins).
The issues may be as simple as bad PCM ground, also check/replace the ASD relay.

XJwonders

Also try this

http://www.naxja.org/forum/showpost.php?p=245993828

Rockfrog

The G106 was the connection I was referring to.

tjwalker

If the vehicle doesn't start and you have a NO BUS, the problem is NOT the dash cluster. The NO BUS with the cluster being a suspect is in play when the vehicle starts. Yours doesn't. Your problem is something along the bus, including all of the 5 volt sensors, wiring and the computer itself.

I'd try disconnecting each and every one of the 5 volt sensors one by one and when that sensor is disconnected, turn the key to the ON position to see if the NO BUS message is gone.

If you do this with all of the sensors and you have no luck, then the problem is most likely a wiring or a computer problem.

caged

i was pulling all the fuses once to see if i had a blown fuse to my brake lights, turns out when i was pulling one by one, i had stuck it in the vacant spot and left an active one open.
as i tried to start the jeep, it just cranked and had no bus on the odo.
i found the problem and switched that fuse and all was good.

can't remember which fuse exactly, but it was on under the dash... maybe yours is blown?

robkee4

Thanks everyone I will try each of these tomorrow and hopefully will have success. I'll reply what worked if it gets solved.

robkee4

Does anyone have a list of all the sensors on the BUS?

CCKen

G106 has nothing to do with this problem.

If anything, it would be G100 or G101.

Rockfrog

Actually the instrument cluster actually has grounds through several points along the line, G101, G106, G107, and G108 ... as per the 2000 FSM (8W-40). There is also a PCM ground at G106. As the instrument cluster is driven by the PCM it was a suggestion based on my personal experiences in the matter. When my No Bus issue came up I cleaned all grounds commonly associated with it (G100, G101, G104), as well as the contacts behind the cluster itself. Then found and obscure reference to G106 and once I cleaned that one my cluster was back up. Hasn't given me trouble since.

robkee4

Can a bad fuel pump cause a no bus code?

tjwalker

Nope.

CCKen

Open this link and scroll down to post #49. It shows the engine bay grounds, and a brief explanation as to their function.

At G101, the 2000 obviously doesn't have an ignition coil here but the ground points are there.

https://www.cherokeeforum.com/f2/gre...e-6558/index4/

There have been cases of a 'No Bus' and disassembly and cleaning of grounds G100 and G101 have fixed the problem.

~~~~~~

Something you can do using a digital voltmeter:

Seperate the CPS connector.

On the body harness side connector of the two connectors, find a pin cavity that has an Orange wire going to it. This is the 5 Volt reference voltage to each of the engine management sensors.

Turn the igintion switch to RUN, but don't crank.

Using the Voltmeter set to 20 VDC, touch the pin cavity with the Orange wire with the (+) probe of the meter and the battery negative post with the meter (-) probe.

You should see 5 Volts +/- 0.5 Volts (with the battery fully charged).

Repeat this process at the TPS connector, and if neccessary, the MAP sensor connector.

If you see less that spec voltage suspect a bad PCM, or high resistance in the wiring. If you see more than spec voltage suspect a bad clockspring. Always wiggle the nearby wiring harnesses to see if the readng changes.

Do this test and get back.

CCKen

By cleaning the grounds at G106 you may have fixed your No Bus sitution because the TCM is grounded at G106. If the TCM is corrupted by a bad ground it may have corrupted the CCD Bus, which may have caused the No Bus...."Bus" as in CCD Bus.

Below is a schematic that shows the modules on the CCD Bus, any of which being corrupted will corrupt the CCD Bus.

Edit: After taking a look at what's grounded where, it looks like the transmission range sensor is grounded at G106 and the TCM is grounded at G101. The range sensor having a bad ground may screw up the TCM however.

robkee4

I have check and cleaned the grounds and also measured the voltage to the sensors with the following results:
Crank position sensor - 0.65v
Cam position sensor - 0.65v
Throttle position sensor - 0.65v
MAP sensor - 0.7v
The battery has a full charge.
Would you believe this leads to the PCM being bad?