[Fixes]
WHT Z06: Fixes

Here is a list of repairs I've done to my Z06.

Fix
Dual Mode Exhaust Solenoid Valve
Brake Pedal Position Sensor
CAGS Replacement
Clutch Pedal Return Spring
Lug Nuts
Parking Brake Cables
Quarter Panel/Rocker Panel Debris
Reverse Lockout Solenoid Replacement
Steering Wheel Position Sensor
Steering Wheel Squeak
Sway Bar End Links
Turn Signal/High Beams Fix
Wheel Bearing Noise

Dual Mode Exhaust Solenoid Valve

When my Z06 reach about 17 years I noticed that the dual mode exhaust would sometimes get stuck in "loud" mode. It got to the point where once the car was warmed up the computer was unable to close the butterflies. These are normally open and engine vacuum is used to close them. The system to control them consists of a class2/J1850 network module, a solenoid valve, a spherical vacuum reservoir, and a vacuum controlled butterfly at each exhaust tip. The ECM commands the butterflies to open for these conditions:

As with other solenoid failures, the intermittent nature of the the failure made me suspect the solenoid valve.

GM Description
25794609 Exhaust Vacuum Control Solenoid Valve (w/tubing)
22902593 Exhaust Vacuum Control Solenoid Valve
25794610 Exhaust Vacuum Control Solenoid Valve

Neither the old nor the new part had GM part numbers on them but the new one came in GM packaging. Both were made by Pierburg:

Part Number Description
7.00953.00 Original
7.00953.01 Replacement

The new Pierburg part number likely corresponds to the change in GM part numbers.

[New Solenoid Valve] [Installed]
New Solenoid Valve Installed

The vacuum lines were really stuck on the old part and it took a bit of force to remove them; I used some dielectric grease when I installed the new part.


Brake Pedal Position Sensor

At around 90K miles I started getting the dreaded "SERVICE ACTIVE HANDLING" along with the the active handling code C0161, symptom 11. I was frequently unable to engage the cruise control or it would drop out for no apparent reason. The factory service manual says the conditions for setting this code/symptom are:

First I tried calibrating the sensor with a Tech2. This teaches the Electronic Brake Control Module (EBCM) where the "foot off" brake pedal position is. When that didn't improve the situation I tried replacing the brake pedal position sensor which was cheap enough.

GM Description
13579090 Brake Pedal Position Sensor (1st design)
10302722 Brake Pedal Position Sensor (my old one)
13597429 Brake Pedal Position Sensor (revised)

Pro-tip from the Corvette Forum: Remove the sensor and bracket as a unit, disconnect the harness, and swap the sensor on the bench; replacing the sensor while still in the car and attached to the bracket is very difficult.

[Brake Pedal Position Sensor]
Brake Pedal Position Sensor

Fun trivia: The brake pedal sensor part number (13597429) is also used as the clutch pedal sensor on the 2nd gen CTS-V Cadillac (2009-2014).

Even after calibrating the new sensor the car kept throwing the code. At this point I eventually figured out that when the cruise control would not engage the brake lights were on! This made a lot of sense and made me want to inspect/clean any connectors between the sensor and the EBCM. However the EBCM is a borg-like assembly of electronics and valves located in the engine compartment and adult hands are too large to get at the connector. Fortunately I spent some time studying the factory wiring diagrams and figured out that the brake pedal sensor connects to the body control module (BCM) which is behind the passenger kick panel and readily accessible. So I disconnected the battery, removed J2, applied dielectric grease to the connector terminals, and reinstalled.

[BCM Connector J2]
BCM Connector J2

I re-calibrated the sensor one final time and that was the end of the problem. Knowing what I know now, next time I would start with the connector …


CAGS Replacement

My T56 transmission has leaked a tiny amount of ATF over the past few years. Googling showed one possible source is the skip shift (aka CAGS) solenoid. Apparently the original design starts to leak internally. One way to solve this is to replace the solenoid with a plug (e.g. the one sold by ICT Billet) but if you do that you'll need to plug an aftermarket skip shift eliminator into the harness or else you'll get an engine check light. But since I use the CAGS LED Fuse method I need the solenoid to be connected and present.

[Original and Replacement]
Original and Replacement

When I removed the old solenoid I found ATF in the connector. Given it has a seal between it and the the transmission case it was pretty obvious that the leak was internal to the solenoid.

Just like the reverse lockout solenoid, the original takes a 34mm deep socket and the replacement a 27mm.


Clutch Pedal Return Spring

After about four years of fun my clutch pedal return spring broke. This was apparently a common problem. Some switched to the C5 Corvette version which is supposed to be softer.

GM Description
12555205 Clutch Pedal Return Spring (C5)
10376347 Clutch Pedal Return Spring

Others liked not having a spring at all. I replaced mine with the original part which has held longer than the original; I suspect there were quality control issues.

[Original] [Replacement] [Installed]
Original Replacement Installed

Lug Nuts

I've yet to meet anyone who like the sheet metal wrapped OEM lug nuts. They are universally hated. It's just a matter of time until your tire technician spins the sheet metal with an impact gun.

When mine started to get in bad shape I picked up a set of Chinese lug nuts from ebay. It's difficult to beat the price but the chrome plating was less than stellar and after a year or two they started rusting.

Eventually I bit the bullet and got a set of McGard 64012 Lug nuts. these are M12 X 1.5. They have a lifetime warranty to not chip, peel, or rust.

[Lug Nuts]
Lug Nuts: OEM, cheap-o, McGard

Parking Brake Cables

I popped a parking brake cable when my Z06 was about ten years old. I guess that's what I get for always using it.

[Parking Brake Assembly]

I decided to replace both cable and given that I found it necessary to remove the exhaust intermediate pipes this was probably the right move.


Reverse Lockout Solenoid Replacement

I started noticing that sometimes reverse was available while driving down the road. This was because my reverse lockout solenoid was failing. I replaced it with the car jack stands. It was not an easy process.

[Original] [Replacement]
Original Replacement

The original solenoid was much larger than the replacement (GM 19178634). The factory service manual calls for a Kent Moore J-41099 (which is a fairly deep 34mm socket) which I didn't have at the time but honestly I'm not convinced there is a enough room to use a ratchet with the transmission still in the car so ultimately I found it easier to remove the entire assembly and replace the solenoid on the bench using a large crescent wrench. I was able to torque the new solenoid in with a 27mm deep socket.

After removal I tested the original solenoid with a suitable 12V power supply; I found that it frequently would stick in the retracted position, which accounted for the symptoms I observed.


Quarter Panel/Rocker Panel Debris

During the first few years I frequently found small rocks and dirt trapped between the rocker panels and the quarter panels. Eventually I found TSB 11-08-65-001A, which is titled, "Information on Small Rocks, Sand and Gravel (Road Debris) Trapped Between Quarter Panel and Rocker Panel and Installing Adhesive Back Shim Stock."

[1 of 4] [2 of 4] [3 of 4] [4 of 4]
1 of 4 2 of 4 3 of 4 4 of 4

I was able to obtain a lifetime supply of the foam tape ("shim stock") from Kent Automotive, it was not difficult to install, and it definitely solves the issue. Although it would not surprise me if it just means that debris is still building up behind the rocker panels …

Part Number Description
P46515 Kent Automotive Shim Stock (9/16" thick, 1" wide)
P46500 Kent Automotive Shim Stock (5/16" thick, 3/4" wide)

Given that this only applies to 2005-2011 Corvettes I suspect Chevrolet started applying foam tape at the factory in late 2011.


Steering Wheel Position Sensor

For a number of years, my Z06 would throw the active handling code C710, symptom 1F. The factory service manual says the conditions for setting this code/symptom are:

In addition symptom 1F is flagged as "intermittent" which was certainly my experience. The code would most offen appear at low speed while moving the steering wheel back and forth a lot, for example when maneuvering in a parking lot.

The first TSB to address this is 06-02-35-002, dated January 2006. It basically says the motion of the telescoping/tilt steering wheel may cause a high resistance condition in the steering wheel position (SWPS) connector. The described remedy is to wrap connector C202 (located on the steering column) in electrical tape and install a zip-tie around the tape. It also says it's important to remove/install the SWPS connector "a minimum of three times to remove any possible terminal corrosion."

My 2007 Z06 already had the tape and zip-tie and so I applied some dielectric grease and reseated the SWPS "a minimum of three times" but it was only a short term solution.

The original TSB was revised in October of 2007 by 06-02-35-002B. It involves installing a new terminal positive assurance (TPA) clip.

GM Description
19179794 Steering Angle Sensor Lead Clip

A TPA is a device that prevents terminals from accidentally coming out of a connector. And it's interesting to note that C202 already had a TPA in place; I believe the new part is a secondary TPA designed to prevent any movement of the terminals in the connector. It also prevents C202 from being disengaged from the SWPS itself.

The next time the car threw the code I decided to bite the bullet and replace the SWPS. This requires removing the steering column from the vehicle which wasn't as difficult as I was expecting.

[Steering Column]
Steering Column

The new sensor was not expensive (~$100) but the factory service manual is unnecessarily intimidating. It references the J-42640 "steering column anti-rot pin" which is a metal rod that is inserted into the steering column to limit rotation of the steering shaft and prevent uncentering and damaging of the SIR coil.

[J-42640]
J-42640

Some have reported not using the tool but to be safe I ordered one. It's 0.2340" in diameter (the same size as an "A" twist drill bit) and honestly a phillips screwdriver of that size or slightly smaller would probably do the job almost as well. In the end the tool limits the steering wheel to about +/- 1/8 of a turn from center.

The new SWPS comes with a pin installed that keeps it aligned. I found I could see inside the hole on the old sensor well enough to know when it was positioned exactly straight ahead. It was a simple matter to swap the sensors and pull the pin out of the new one.

GM Description
15231656 Steering Wheel Position Sensor (w/telescopic)

The new SWPS appears to have solved my issue. Inspection of the old sensor revealed a small buildup of black powdery residue; I suspect it was just worn out.

[Old SWPS] [New SWPS]
Old Steering Wheel Position Sensor New Steering Wheel Position Sensor

Steering Wheel Squeak

Recently my steering wheel started to squeak. The solution was to remove the steering wheel and spray a little silicone into the small gap between the plastic rotating parts.

[Steering Wheel SIR Coil]
Steering Wheel SIR Coil

Sway Bar End Links

When my Z06 was about five years old I started noticing a clicking sound coming from the suspension when driving over driveways. This was reported on the Corvette Forum to be do to the sway bar end links.

[Sway Bar End Link]
Sway Bar End Link

I bought and installed replacements which fixed the noise.

GM Description
20822934 Suspension Stabilizer Shaft Link

Eventually TSB PIC4475B was issued, "Snap Clunk Noise From Front Or Rear Of Vehicle - keywords click link noise snap stabilizer stable suspension." It suggests replacing any end links that make noise.


Turn Signal/High Beams Fix

Around 90K miles I noticed that sometimes my high beams would come on when making right turns. This turned out to be a well documented problem with the turn signal (aka multifunction switch).

[Multifunction Switch] [Installed]
Multifunction Switch Multifunction Switch Installed

Removing and reinstalling the steering column trim is the most difficult part of the job.

GM Delco Description
20808029 D6244E Turn Signal, Headlight, Headlamp Dimmer, etc. Switch

Wheel Bearing Noise

After about ten years of fun I started noticing an obvious wheel bearing noise coming from the rear. My best guess was that it was the left rear. using a Steelman "Chassis Ear" box I was able to definitely identify wheel (it was opposite from my guess).

[Wheel Bearing]
Wheel Bearing

As recommended I replaced the axle shaft nut, applied Loctite 272 and torqued to 160 lb/ft.

GM Delco Description
88967288 RW20-86 Rear wheel hub
10257766   Rear axle shaft nut

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Craig Leres