Anyone successfully fix a 71 code? (1 Viewer)

[Sev65]

I'm getting a engine light with a 71 code. It always seems to come on under the exact same conditions (driving a long stretch at a set speed and rpm and never with stop and go).
Truck runs good overall except for a slight rpm drop at long stop lights when hot.

I've done some searches and haven't found a thread with a successful repair result.

Has anyone ever fixed this code?

 

[LAMBCRUSHER]

I'm getting a engine light with a 71 code. It always seems to come on under the exact same conditions (driving a long stretch at a set speed and rpm and never with stop and go).
Truck runs good overall except for a slight rpm drop at long stop lights when hot.

I've done some searches and haven't found a thread with a successful repair result.

Has anyone ever fixed this code?

I have not...but I'm not going to spend hundreds on sensors and switches if it isn't going to work. I am thinking about finding a non Cal ECM and seeing if that'll work, but I'm guessing it'll open another can of worms- compatability diffs between the 2 sets of logic. I do my best to ignore it, check to make sure it is the code 71 again from time to time(so I don't miss any new ones or odd balls) and reset the efi comp by yankin the fuse for 30 seconds every now and again. I think it's been about 3 weeks now since I've seen it. wonder if just sending the computer in for a refurbish would do the trick. ANyway, I'd like to hear about success here as well.

 

[Sev65]

Lambcrusher, are you getting the light under the same driving conditions as me?
I've tried testing and cleaning the egr with no luck. I think my next step is to test those 3 little egr solenoids.

 

[LAMBCRUSHER]

Lambcrusher, are you getting the light under the same driving conditions as me?
I've tried testing and cleaning the egr with no luck. I think my next step is to test those 3 little egr solenoids.

yes, exact same conditions. shorter drives thru the hills- even longer in the hills, and no fault condition, but after some time cruising down in the flats- particularly on my way home from the big city, at almost the exact same spot, or within say 10 miles thereof, I get CEL. same code every time. When I first got the rig, it would fire off the 25 and 26, so I changed the O2 sensors for new densos. I would occasionally get the same 25/26 for a short time there after, but that stopped when I re-wired the fusible links. the wiring harness for the EGR sensor checks on my rig- I didn't check the VSVs tho- good call, maybe they aren't opening/closing the valve at the proper moments in time and the sensor is actually getting a low gas temp reading let's keep at this and compare notes, huh?

 

[Sev65]

yes, exact same conditions. shorter drives thru the hills- even longer in the hills, and no fault condition, but after some time cruising down in the flats- particularly on my way home from the big city, at almost the exact same spot, or within say 10 miles thereof, I get CEL. same code every time. When I first got the rig, it would fire off the 25 and 26, so I changed the O2 sensors for new densos. I would occasionally get the same 25/26 for a short time there after, but that stopped when I re-wired the fusible links. the wiring harness for the EGR sensor checks on my rig- I didn't check the VSVs tho- good call, maybe they aren't opening/closing the valve at the proper moments in time and the sensor is actually getting a low gas temp reading let's keep at this and compare notes, huh?

You got it. I'm in the process of remodeling my garage but when I finish I gotta get the cruiser in and really try to figure this thing out.

 

[Inukshuk]

See https://forum.ih8mud.com/80-series-tech/12498-egr-problem.html

 

[Sev65]

Just wanted to follow up with what I came up with on the 71 code.

I went in for a smog test and failed with high nox. I started doing some testing per the fsm and found my egr was not opening when need. The 71 code is for incorrect exhaust temp reading which iirc is CA emission trucks only hence the lack of info on the code.

Long story short all the components tested out fine but my egr was still inop. After going through all the emission vacuum lines I found one crossed behind the intake manifold. Bingo egr works, passed smog, check engine light gone.

If anyone is reading this and has a intermittent 71 code I'd suggest you start by making sure the egr works per the fsm. What the 71 code basically means is that the exhaust temp sensor isnt reading the proper temperature at a specific time. This would more that likely be caused by a failed temp sensor (mounted on egr valve) or an inoperable egr system (valve,modulator,vsv,lines).

The tests are all in the fsm and are very easy to perform, You'll need a vacuum gauge. Having a mityvac will make it much easier to test things.

hope this helps.

 

[schmoman]

Has anyone ever fixed this code?

Got a 71 code at highway speeds after a about 10 minutes. Decided to pull my EGR valve. Ran some throttle body cleaner through the metal parts and chipped away at the grime. Also took a wire brush to the EGR sensor after unscrewing it from it's mounting. The grime on there was about 2mm thick.

Did this and never had code 71 since.