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Old 09-04-2018, 11:13 AM   #1
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Join Date: May 2000
Location: Alexandria, LA 71301
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Question OBD code 21 & 87

My 94 Cheyenne 350/4L60E has 2 codes, 21-TPS signal high, and 87-EEPROM flash memory error. On 21, I changed the TPS (housing was cracked) before it had this problem, and all was well for a short time then truck started stumbling off-idle and idling high. Also What are effects of 87? No vacuum leaks, no miss, just hesitation & high idle. I notice a difference in shift points also. Anybody?
-02 avalanche (daily driver)
-66 gto ragtop 389/400 (garage queen, hand-me-down from dad)
-72 Tribute Trans Am (6.0LS/T56 6-speed) in progress
-2003 YUKON (Wife's)
-71 gmc swb fleet (current project, gonna shave everything, bags, stuff w/ 20's, gen III powertrain)
-94 Cheyenne (350/4L60E) 5/6 drop JUST FOR FUN
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Old 09-11-2018, 03:23 PM   #2
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Re: OBD code 21 & 87

Still having the issue?
Have you tried hooking up a vacuum gauge and seeing whats it says?

Saw this on another post, may help you get started. Hesitation can be a few things but good to start with a vacuum gauge.
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Old 09-16-2018, 01:58 PM   #3
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Re: OBD code 21 & 87

Check the 10 amp fuse in the fuse panel labelled Trans...87 code can be set if this fuse blows...
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