I've got a 1991 F150 with the 4.9. I recently bought a code reader and checked for koeo codes. I found one for egr and o2 so I fixed those 2 issues now then got the code 11 for system ok. Then I ran the KOER test and got a code 18 r for the spout. So I replaced the tfi and I took it down the road, ran pretty except for slight hesitation when taking off and a choppy low idle about 700 rpm. It's still throwing the code 18 and the spout is connected. Wondering what the next thing to check would be?

 

Scanners for these trucks are notoriously UNreliable - they frequently display spurious codes & vague or irrelevant definitions. I recommend you return it for refund, and use a simple jumper wire, as shown here:


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Don't pick a word or part name out of a code definition. When you post a code, post the whole number and the COMPLETE definition. Codes do NOT mean to replace parts - they only indicate where to BEGIN diagnosis. The diagnostic procedure for this fault is in Haynes Ch.5, Sec.5 or 7 (depending on which edition you get). It requires a digital multimeter, some jumper wires, pierce probes, and patience.


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Since you now know that the ICM wasn't the problem, I recommend you put the original back. It's probably higher-quality than the new one (which you might still be able to return for refund).

 

The old tfi looked pretty nasty on the inside. Looked like it had gotten some moisture in it because the board had rust in several points. The one I swapped for it came off of a parts truck that I have with lower miles and same year. Parts truck was a great investment lol. I'll try out the jumper method to see if I yield different results. If not Ive got a Haynes laying around and a multimeter. I'll post my results asap.