diagnostic help
Thread Starter
Instructor
Joined: Nov 2004
Posts: 148
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From: Ashland, Kentucky
diagnostic help
Check engine light comes on while driving. It goes off when idling. Jumpered the aldl and pulled a DCT H26, LCD blanking control circuit (circuit shorted to battery voltage or CCM internal open). It sounds pretty crappy. Is there anyone that has experience with this problem, is it common? This just started. Do I need to take it to a pro? 95 auto
Team Owner
Joined: Aug 2000
Posts: 40,156
Likes: 45
From: San Pedro CA
Not to sound ignorant, but the best tool for a problem like this is a copy of the Helm Factory Service Manual - www.helminc.com.
You might find used copies on eBay or even here in parts for sale.
These kinds of problems usually include several diagnostic steps that will take you through the circuit... and determine the exact problem.
I am curious that a H26 on the PCM would point to the CCM like that. I would expect that kinda code to appear in the SYS module (on the speedometer).
You might find used copies on eBay or even here in parts for sale.
These kinds of problems usually include several diagnostic steps that will take you through the circuit... and determine the exact problem.
I am curious that a H26 on the PCM would point to the CCM like that. I would expect that kinda code to appear in the SYS module (on the speedometer).
Thread Starter
Instructor
Joined: Nov 2004
Posts: 148
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From: Ashland, Kentucky
got the Helms. Just was curious if anyone had the same problem, and if so where did they find the short. Helms says to check voltage at the instumentation harness. Look for shorts. Or replace instrument panel. If those check out ok it says to call help line for ccm help!
Thread Starter
Instructor
Joined: Nov 2004
Posts: 148
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From: Ashland, Kentucky
Helms manual also says that if this fault is present the LCD portion of the instrument cluster will be blank. Mine is fine, the only problem I am having is that dang check engine light.
Team Owner
Joined: Aug 2000
Posts: 40,156
Likes: 45
From: San Pedro CA
that's what is confusing me... the SES is for the PCM, this error sounds more like a CCM kinda problem.
I don't understand why the SES would be reporting this error.
Can you cross reference that code to a different error listing?
I don't know the error structure of the 1995 as well as I should...
I don't understand why the SES would be reporting this error.
Can you cross reference that code to a different error listing?
I don't know the error structure of the 1995 as well as I should...
Burning Brakes
Joined: Jun 2004
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From: richardson tx
although your code is a history code this may help.. 1995 Chevrolet Corvette V8-350 5.7L VIN P MFI
CIRCIUIT DESCRIPTION
The LCD blanking control circuit carries a signal which allows all segments of the LCD to be turned "OFF" simultaneously, its purpose is to allow the CCM to blank the LCD panel with a single signal.
DTC 26 WILL SET WHEN
The CCM has requested the circuit to be low, 600 ms has passed and the CCM senses a high voltage in CKT 1374.
ACTION TAKEN (CCM WILL DEFAULT TO)
Sets a DTC 26 and flashes the "SYS" indicator.
DTC 26 WILL CLEAR WHEN
The CCM no longer senses a high voltage in CKT 1374 when it is requesting the circuit to be low or the CCM is no longer requesting the circuit
to be low.
DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number{s) on the diagnostic chart.
l. Checks for a good signal to the instrument cluster from the CCM'
2. Replaces The clusters pull-up resistor and voltage reference to allow testing of the CCM. If the DTC comes back the CCM is probably at
fault. If the DTC does not come back, the cluster is probably the source of of the problem.
3. Checks for another DTC being set. If that DTC was set, it is possible that the problems which set that DTC also set this one'
DIAGNOSTIC AIDS
if this fault is present, the LCD portion of the instrument cluster will be blank. If the DTC is a history DTC, the problem may be intermittent'
Try performing the tests shown while “wiggling" wiring and connectors, this can often cause the malfunction to appear. Refer to "Intermittents
and Poor Connections" in DIAgRAMS.
Copyright O 2006, ALLDATA 8.80 Page 2
CIRCIUIT DESCRIPTION
The LCD blanking control circuit carries a signal which allows all segments of the LCD to be turned "OFF" simultaneously, its purpose is to allow the CCM to blank the LCD panel with a single signal.
DTC 26 WILL SET WHEN
The CCM has requested the circuit to be low, 600 ms has passed and the CCM senses a high voltage in CKT 1374.
ACTION TAKEN (CCM WILL DEFAULT TO)
Sets a DTC 26 and flashes the "SYS" indicator.
DTC 26 WILL CLEAR WHEN
The CCM no longer senses a high voltage in CKT 1374 when it is requesting the circuit to be low or the CCM is no longer requesting the circuit
to be low.
DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number{s) on the diagnostic chart.
l. Checks for a good signal to the instrument cluster from the CCM'
2. Replaces The clusters pull-up resistor and voltage reference to allow testing of the CCM. If the DTC comes back the CCM is probably at
fault. If the DTC does not come back, the cluster is probably the source of of the problem.
3. Checks for another DTC being set. If that DTC was set, it is possible that the problems which set that DTC also set this one'
DIAGNOSTIC AIDS
if this fault is present, the LCD portion of the instrument cluster will be blank. If the DTC is a history DTC, the problem may be intermittent'
Try performing the tests shown while “wiggling" wiring and connectors, this can often cause the malfunction to appear. Refer to "Intermittents
and Poor Connections" in DIAgRAMS.
Copyright O 2006, ALLDATA 8.80 Page 2
