New CEL Imponderable

[imp]

Been here a lot lately, solved "Forced Limited Power" issues, but retain ABS light ON, that seems to have no effect, "VIN Mismatch". Now, a new CEL after a couple hundred miles. Hoping the Gurus here will help.

P0054 "HO2S Heater Resistance, B1, Pos 2"; P0060 "HO2S Heater Resistance, B2, Pos 2". Both throw at the same time. Delete, come back. 153K, so replaced all 4 Oxygen sensors. Old sensor heater resistance was within spec., which said 3 to 40 Ohms, I had 5 Ohms Upstreams, 9 Ohms Downstreams. Drove 120 miles, same DTCs back.

Found an on-line source which made sense, a little. First, I wondered why both banks would go bad simultaneously, two sensors at same time, nah! Harness faults? Unlikely, as PCM looks at the sensors individually. Site said "Intake Air Leaks" a possible cause.

How about this, guys? I'll reveal that in the process of tracking down possible Throttle Body problems, I had the T.B. on and off maybe 6 times, it's gasket (spacer) looked reusable, has a thin white O-Ring on either side, maybe Teflon. That baby might just be leaking a bit? Ordered a new one, not a common stock item around here, nobody had one, O'Reilly said 2 weeks! If no opinions, or facts come up, I'll be back after I install the new one. Thanks fer readin'! imp

EDIT: 2004 Ex., 4.0L "K" Eng. (Flex-Fuel), 4X4, 5R55S

 

[Rick]

Maybe a leaky intake manifold gasket? It's not unheard of on the 4.0.

 

[rocco123]

Common power wire shorted?

 

[imp]

Maybe a leaky intake manifold gasket? It's not unheard of on the 4.0.[/QUOTE]

I've heard that too. I had the upper intake off about 2 years ago to replace the Fuel Pressure and Temperature Sensor, replaced the gaskets at that time. No idea about the lower manifold-to-heads gaskets, though. Near impossible to get in down there with anything to indicate leakage. imp

 

[imp]

Common power wire shorted?

Wondered about that, too. A short to ground of the hot feeder to the Oxygen Sensors would also knock out power to the PCM, EGR module, Vapor Management Valve, and Evap. Canister Vent Valve. Would'nt run at all. An open in the hot lead feeding the HO2S sensors, depending on where it occurred, would completely cut power to the heater(s). Don't think the PCM would let it run over a hundred miles that way.

It's a baffler! Thanks for help! imp

 

[imp]

Well, here's the new T.B. gasket results: < 50 miles driven, CEL back ON, same DTCs! How to check for lower and upper intake air leakage? imp

 

[rocco123]

From what I've read, you look for a change in idle while holding an unlit propane torch by the manifilold. If idle speed changes, you found your leak. You might try attaching a rubber hose to the tip so it will fit into tighter areas.

 

[imp]

Well, here's the new T.B. gasket results: < 50 miles driven, CEL back ON, same DTCs! How to check for lower and upper intake air leakage? imp

Best suggestion I've heard yet! The propane gets burned as extra fuel which should real quickly speed up idle, but not for long, as the PCM detects that fast. If no change in speed, no leak! I like it! Thank you.

Problem with the German-built engine is accessibility, so damn hard to get at those gasket surfaces.
imp