C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Code Definition

Thread Tools
 
Search this Thread
 
Old May 28, 2025 | 10:23 PM
  #1  
CorvetteRules's Avatar
CorvetteRules
Thread Starter
Drifting
Liked
Loved
Community Favorite
Top Answer: 1
 
Joined: Nov 2018
Posts: 1,787
Likes: 579
From: Mays Landing, NJ
Default Code Definition

I'm showing two H codes on my 95. One is 72 which my understanding is just from the after market radio that was installed. The other is 74 which I'm finding multiple explanations for. Do any of you have information on what 74 indicates?
Reply
Old May 29, 2025 | 11:47 AM
  #2  
IHBD's Avatar
IHBD
Melting Slicks
All Eyes On Me
Shutterbug
Top Answer: 5
Pro Mechanic
 
Joined: Nov 2016
Posts: 2,235
Likes: 3,063
From: So Cal
2023 C4 of the Year Finalist - Unmodified
Default

If the H72 and H74 are in Module 1, H72 is LCD lighting, and H74 is LED lighting. "LCD" is the backlighting in the radio and HVAC displays. H72 should only show up on aftermarket radio installation if the car has C60 MANUAL HVAC controls. In a C60 car, there is no LCD display, so removing the radio leaves no LCD backlighting. << This is the situation where the "resistor fix" applies.

H74 Module 1 are the green LED lights above the buttons. HVAC, Fog Light switch, and the radio. My 92 frequently has 1.H74 set, but not always. I ignore it and clear it.

H74 also exists in Module 4 and Module 9. 4.H74 is TCS circuit Low, and 9.H74 is Low Voltage at the TCS/ABS module.

Knowing, and reporting which module the codes are in is important. But almost no one on here ever does. (One guy took a video of his screen for the entire read-out sequence. I found that incredibly helpful.)

Last edited by IHBD; Jun 3, 2025 at 04:48 PM.
Reply
Old May 29, 2025 | 05:19 PM
  #3  
CorvetteRules's Avatar
CorvetteRules
Thread Starter
Drifting
Liked
Loved
Community Favorite
Top Answer: 1
 
Joined: Nov 2018
Posts: 1,787
Likes: 579
From: Mays Landing, NJ
Default

Thanks for the information, I'll pull the codes again and pay attention to what module the 74 shows up under. Not worried about the 72 because the radio was replaced by a Pioneer by the PO. Based on the information you provided it appears that regardless of what Module the 74 shows up in it would not be what is is causing my current starting but stalling seconds later. Do you agree with that?
Reply
Old May 29, 2025 | 06:15 PM
  #4  
IHBD's Avatar
IHBD
Melting Slicks
All Eyes On Me
Shutterbug
Top Answer: 5
Pro Mechanic
 
Joined: Nov 2016
Posts: 2,235
Likes: 3,063
From: So Cal
2023 C4 of the Year Finalist - Unmodified
Default

I agree that none of the possible 72 or 74 DTCs will cause your starts but dies.

I put a response in your other thread. Cheers.
Reply
Old May 30, 2025 | 11:46 AM
  #5  
Natty C's Avatar
Natty C
Melting Slicks
Community Builder
Community Influencer
Community Favorite
Top Answer: 1
 
Joined: May 2019
Posts: 3,173
Likes: 1,375
From: Mid-Atlantic
2025 C4 of the Year Finalist - Unmodified
2023 C4 of the Year Finalist - Unmodified
2022 C4 of the Year Finalist - Unmodified
2021 C4 of the Year - Unmodified Finalist
Default

Originally Posted by IHBD
If the H72 and H74 are in Module 1, H72 is LCD lighting, and H74 is LED lighting. "LCD" is the backlighting in the radio and HVAC displays. H72 should only show up on aftermarket radio installation if the car has C60 MANUAL HVAC controls. In a C60 car, there is no LCD display, so removing the radio leaves no LCD backlighting. << This is the situation where the "resistor fix" applies.

H74 Module 1 are the green LED lights above the buttons. HVAC, Fog Light switch, and the radio. My 92 frequently has 1.H74 set, but not always. I ignore it and clear it.
This is the first time I've ever seen these two codes explained thoroughly enough to be a meaningful difinitive explanation. Thanks!
Reply

Get notified of new replies

To Code Definition





All times are GMT -4. The time now is 08:39 PM.

story-0
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!

Slideshow: The 10 most explosive Corvettes ever built based on power-to-weight ratio.

By Joe Kucinski | 2026-05-20 07:23:03


VIEW MORE
story-1
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter

Slideshow: From C1 to C8 we compare every Corvette generation by the numbers.

By Joe Kucinski | 2026-05-12 16:54:12


VIEW MORE
story-2
8 Coolest Corvette Pace Cars (and Replicas) of All Time

Slideshow: Some Corvette pace cars became collectible legends, while others perfectly captured the look and attitude of their era.

By Verdad Gallardo | 2026-05-11 09:50:51


VIEW MORE
story-3
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)

Slideshow: Ranking the top 10 Corvette engines by torque output.

By Joe Kucinski | 2026-05-05 11:58:09


VIEW MORE
story-4
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!

Slideshow: A Corvette pace car nearly matching IndyCar speeds sounds exaggerated, until you look at the numbers.

By Verdad Gallardo | 2026-05-04 20:03:36


VIEW MORE
story-5
Top 10 Corvettes Coming to Mecum Indy 2026!

Among a rather large group of them.

By Brett Foote | 2026-05-04 13:56:44


VIEW MORE
story-6
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!

Slideshow: the top 10 things Corvette owners want in the C9 Corvette

By Michael S. Palmer | 2026-04-30 12:41:15


VIEW MORE
story-7
10 Revolutionary 'Corvette Firsts' Most People Don't Know

Slideshow: 10 Important Corvette 'firsts' that every fan should know.

By Joe Kucinski | 2026-04-29 17:02:16


VIEW MORE
story-8
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2

Slideshow: Should you buy a 2020-2026 Corvette or wait for 2027?

By Michael S. Palmer | 2026-04-22 10:08:58


VIEW MORE
story-9
2027 Corvette vs The World: Every C8 vs Its Closest Competitor

Slideshow: 2027 Corvette lineup vs the world.

By Joe Kucinski | 2026-04-24 16:12:42


VIEW MORE