2001 XJ - "no bus" issue

[anthrax323]

Hey all,

Been absent a while (been a hell of a few years), but I finally got my 2001 XJ back together after a mini-stroker build I completed a few years ago... I'm pretty close to firing it up to break in the cam, but have hit the "no bus" issue.

Fuel pump relay has been pulled in order to prime the engine oiling before actually firing it up. Engine's block heater has been plugged in overnight, and the head temp just behind the thermostat housing is reading 152°F (higher than I expected).

When the key is turned to the "on" position and I get the chime, I've noticed the following symptoms (before the "no bus" error appears along with the CEL after about 30 seconds):

• Oil pressure needle moves a tiny bit, up to the 0 mark. Even when cranking (total of maybe 30 seconds thus far) it does not move past this.
• Coolant temp gauge does not move at all (should absolutely read something with the engine having been heated).
• Voltage gauge does not move at all.
• Fuel level gauge does not move (pretty sure all the gas evaporated over the last 6 years anyway).
• No connection is made via an OBD2 scanner.

I've disconnected the CPS (brand new, Mopar) with no changes in symptoms.

I've also verified every connection both in the engine bay (particularly the 3 large ones that connect the engine and drivetrain harnesses to the body harness, along with the ECU connections) and under the vehicle... no dice.

What the hell am I missing here? Nothing was taken apart in the interior of the vehicle when doing this engine build/swap.

I feel like I'm missing something stupid, but after all these years, it's escaping me. Thank in advance.

 

[anthrax323]

Following diagnostic suggestions in this thread, I checked the voltage at the TPS with the key in the "on" position... and got 5.17v on the orange/reference wire (which is good). Battery is reading 12.54v at the terminals.

All fuses in the underhood PDC/fusebox are good. Reinstalled the fuel pump relay for giggles... and I can't hear it cycle when I turn the key to "on". Curious if this is related, or if it's just been sitting too long.

 

[anthrax323]

Also getting no voltage (<0.1v) across pins 3 and 11 (CCD bus pins) in the OBD2 connector.

 

[anthrax323]

Aight, another stream-of-consciousness update. I went and re-tested pins 3 and 11 on the OBD connector and got ~2.4v on each when testing against a ground (as one should). Upon doing so, I looked up to see that the other gauges (fuel, temp, voltage) were now working, and the "no bus" error went away.

Now, with the fuel pump relay installed, I'm still not hearing it nor getting any fuel pressure (despite the tank showing 1/4 full). Hooray for progress of some sort.

 

[RCP Phx]

Have you seen/read the TSB that was issued 20+ years ago?

 

[anthrax323]

Have you seen/read the TSB that was issued 20+ years ago?

Glad to see you’re still around, man. And possibly, but I have no clue which one you’re referring to.

 

[RCP Phx]

It was a TSB on a "no buss" issue due to the tension/pulling on the cable to the instrument cluster.

 

[anthrax323]

It was a TSB on a "no buss" issue due to the tension/pulling on the cable to the instrument cluster.

Ahh, gotcha. Fortunately it’s no longer an issue (magic, I say). New issue is the fuel pump… gonna go out and do some more diagnostics once the sun goes down a bit and a friend is available to assist. Fuel pump relay passes bench tests so at least I can rule that out.

 

[guero_gordo]

I got this message when I switched the car on with the engine removed. You didn't by any chance forget you had pullet the motor did you? ;-)