Code 62 ASR Service and Tach boouncing
09-15-2005, 10:27 AM
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Code 62 ASR Service and Tach boouncing
92 vette ASR Service light comes on after about 3 minutes of driving and tach starts to bounce and not work. Any ideas. Installed an new tach filter and problem is still there. Any new ideas.
Last edited by JC4; 09-23-2005 at 03:18 PM.
09-15-2005, 11:59 AM
#2
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Do a search. About 2 weeks ago, there was a 4 or 5 page thread about this exact same problem.
If I remember right, it was a problem with the tach filter. (That 2 wire box coming from the ICM on your ignition coil). Suggestion, replace the ICM and the tach filter. (Replace the tach filter first, then the ICM is the problem does not elevate.)
In the HELMS manual, looking up code H62 is "Low Tach Pulse", and it warns in a small "Note:" paragraph, that serious drivability issues can result if "there is an open ground on the ignition side of the filter" (meaning the side that is sent to the ECM.
Apparently the tach filter "cleans" the "crude" signal from the opti side, sends it to the ECM for the tachometer, ASR system control, and back out to the ICM for coil detonation to the optispark distributor. A faulty tach filter will send a distorted or out of spec signal to the ECM, which will cause your tach to bounce around all over the place, your ASR system to malfunction (from a "Low Tach Pulse") and throw a "Service ASR" light, and eventually, it can cause your ICM to loose the reference pulse which, of course, shuts down the coil and finally no spark to the opti for distribution. Many times, it can cause a no start situation.
Recommendations: Replace the tach filter (just to be safe) and check the area for any loose or open grounds. There is a bolt, right above the water pump, on the passenger side, bolted into the passenger head/intake region that has a star washer with a ground wire for either the ICM or tach filter, or both. I know, in time, the bolt can vibrate loose and cause an intermittent ground. Check to make sure all ground bolts are tightened, no open grounds, and replace your tach filter.
Hope this helps! Take Care!
If I remember right, it was a problem with the tach filter. (That 2 wire box coming from the ICM on your ignition coil). Suggestion, replace the ICM and the tach filter. (Replace the tach filter first, then the ICM is the problem does not elevate.)
In the HELMS manual, looking up code H62 is "Low Tach Pulse", and it warns in a small "Note:" paragraph, that serious drivability issues can result if "there is an open ground on the ignition side of the filter" (meaning the side that is sent to the ECM.
Apparently the tach filter "cleans" the "crude" signal from the opti side, sends it to the ECM for the tachometer, ASR system control, and back out to the ICM for coil detonation to the optispark distributor. A faulty tach filter will send a distorted or out of spec signal to the ECM, which will cause your tach to bounce around all over the place, your ASR system to malfunction (from a "Low Tach Pulse") and throw a "Service ASR" light, and eventually, it can cause your ICM to loose the reference pulse which, of course, shuts down the coil and finally no spark to the opti for distribution. Many times, it can cause a no start situation.
Recommendations: Replace the tach filter (just to be safe) and check the area for any loose or open grounds. There is a bolt, right above the water pump, on the passenger side, bolted into the passenger head/intake region that has a star washer with a ground wire for either the ICM or tach filter, or both. I know, in time, the bolt can vibrate loose and cause an intermittent ground. Check to make sure all ground bolts are tightened, no open grounds, and replace your tach filter.
Hope this helps! Take Care!
Try a new Tach Filter
