none of the O2 heaters work? | Ford Explorer Forums - Serious Explorations

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none of the O2 heaters work?

pufferfish

Well-Known Member
Joined
December 9, 2006
Messages
278
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City, State
Baltimore
Year, Model & Trim Level
97 Mounty 5.0
I need some help diagnosing a problem. I am short on time, so tracing wires and hunting for diagrams would be slow going. So, I am throwing it out to the community in the hopes that someone can help identify the issue.

BACKROUND: 97 mounty I just put a 347 into. I used a rebuilt 4r70w trans from a 98 and found out when plugging in the trans wiring harness (which has 3 of the 4 O2 sensors), that the shift lever sensor doesn't plug in. I bought a new one for a 97 and got a 98? same item showed up on every site, but found the right one from a 96 F150. then found out in my searching, that the internal electrical stiff is different too. I found a diagram to repin the internal trans connector to work with the 98 trans and performed the repin job. it wasn't too difficult. I did end up with 2 or 3 (can't remember off hand) extra power wires that weren't being used with the 98 trans, so I just pinned them to the non-used spots in the connector to keep it clean.

WHATS HAPPENING: ok, so the engine starts and runs. I took it for a slow drive around the block and all gears shift perfectly, so I am certain I did the repin correctly. but its got no power and stumbles with the slightest touch of the gas and I have a slew of codes.
P0135 (o2 heater b1,s1)
P0141 (o2 heater b1, s2)
P0155 (o2 heater b2, s1)
P0161 (o2 heater b2, s2)
P0171 (system too lean)
P0453 (evap press high)
P1000(system readiness not complete)

From reading, the O2 heater issues may be the main problem with power. heaters inop will cause improper readings and the PCM will adjust the fuel tables to compensate.

I looked for a blown fuse that may be related to the heaters, but all fuses are in good working order. I didn't modify any of the O2 sensor wiring in the trans harness, so unless one of the extra power wires that were not needed for the trans controls was somehow supposed to power the heaters, it should work, right?

any suggestions? like I said, I have very little time these days, so I am hoping to avoid tracing wires. if someone can tell me what pins to check and for what, it would really help a lot.
 



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A little bit of digging around makes me think the 96 F-150 uses a single ground wire for both the signal and heater while later years use two separate grounds.

I'd check the continuity of the ground wires for each harness.
 






Harness is 97 mounty. I just had to get a 96 f150 shift lever sensor to get the right one.

The mounty harness has 4 wires per o2. On another note, I looked in my Haynes manual and it says fuse 11 gives power to the heaters. That doesn't correlate to reality though. I did test the connectors at the sensor and it should be 12v with key on-engine off. No power. Need to find why there is no power. Wish I knew where the heater power wires all joined together. I could trace it from there pretty easily.
 












That diagram is a carbon copy of the Haynes. There is no 15 amp fuse 11 in the power dost box or the interior panel.

You are right, I could just give one of those wires ko power and make it work. My concern is if I give it power with whatever is messed up, it might kill the PCM or something else?
 












The power dist is what I was calling the one in the engine bay. That diagram is interesting. I do have a 20a fuse there. It does, however, have power. I will have to check continuity to the trans harness.
 






that #11 20amp fuse was for the hego. when I tested the fuse terminal, it had power, but I pulled the fuse this morning and found the hot side was loose. I tightened it back up, cleared the codes and went for a test drive. ALL the codes are gone and the truck runs much better! now to get some good gas (has sat for 8 months) and work on getting her tuned!

thanks for the help!
 












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