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C4 PKE DOA
Q: I read and followed the suggestions in your "C4 Keyless Entry and Alarm Repair" columns, which were a great help in troubleshooting. The results weren't quite what I wanted, but maybe I missed something along the way. My car is a '96 model with the 16-pin ALDL.
The error code I obtained during testing was one blink followed by three (Code 13). I checked the battery (which was good), tried two fobs, shook both fobs like crazy, reprogrammed the system, and tried all the other simple suggestions. No change.
While the PKE system won't work, the alarm seems to, as long as the door locks are set. On occasion, the alarm will arm when I leave the car unlocked. The car never unlocks automatically.
At this point I'm afraid might have to get into a serious disassembly project, which at my age (64) is a pain!
Is there any other test I might try to find out what the problem is? Could it be a sensor in the door, as opposed to the receiver under the dash? Could the problem related to the computer itself?
Thank you for a great magazine and all the up-to-date articles.
A: The Passive Keyless Entry (PKE) system on the C4 Corvettes can make you want to pull out your hair. From your description and the presence of Fault Code 13 (Transmitter Not in Range), I believe you either have a dead battery in your transmitter, or the transmitter has an internal failure. (They've been known to develop loose solder joints over time.)
PKE Transmitter Battery
Let's start by reviewing the process for replacing the transmitter battery.
1. Insert a pocket screwdriver or dime-size coin into the slot on the back of the transmitter and gently pry apart the two halves.
2. Gently pull the battery out of the transmitter and clean the inside of the transmitter with a spray contact cleaner.
3. Inspect the transmitter for broken prongs. This is a common failure.
4. Place the new battery (type CR2032 or equivalent) in the transmitter. It's held in place by two retaining clips and can be difficult to install. The easiest method is to hook the battery into the bottom retainer first and then press it into the top one.
5. Reassemble the transmitter.
6. Test the transmitter.
A weak battery will reduce the operating range of the PKE. If you've noticed that you need to be closer to your vehicle for the transmitter to function, it's possible that the battery is getting weak.
Replacing the battery in your transmitter does not require the transmitter to be reprogrammed to the PKE receiver. However, a new transmitter, or any additional transmitters, will need to be programmed.
PKE Transmitter Programming
The PKE system is capable of using three different transmitters, with each one having its own distinctive VAC (Vehicle Access Code). The transmitter-programming mode is initiated by entering a specific button sequence on the DIC (Driver Information Center, shown at left). Use the following steps:
1. Move the transmitters to be programmed at least 12-15 feet away from the car.
2. Turn the ignition to the run position (engine off).
3. Push the TRIP ODO button once and release it (Image A).
4. Push the TRIP ODO button again and hold it for five seconds.
5. Within five seconds, push and hold the FUEL INFO button for 10 seconds, at which point the PASSIVE KEYLESS ENTRY lamp should illuminate constantly (Image B).
6. Turn the ignition key to the locked (off) position, with the key remaining in the ignition. The passive keyless system lamp should flash once per second, signaling that the system is ready to program the first transmitter. The number of times the light flashes corresponds to the number of the transmitter you're programming—once per second for the first transmitter, twice per second for the second transmitter, and three times per second for the third transmitter.
7. Bring the transmitter to be programmed into range. (Bringing more than one transmitter into range at a time will make it difficult for the system to search for individual codes.)
8. The PASSIVE KEYLESS ENTRY lamp should come on and stay on, signaling that the code has been stored.
9. Move the transmitter out of range. The system light will flash again, indicating that it's ready for the next transmitter.
10. You can exit the programming mode by removing the key from the ignition or by turning on the ignition.
Exiting this mode before you program any transmitters will not cancel or "erase" any transmitters that were programmed into the system previously. The programming mode will automatically shut off after two minutes if no transmitters have been programmed or the key is removed.
If these steps don't work, the most likely cause of your problem is a failed PKE module inside the car.
Thanks for the question, and let us know how it works out.
Needs to Chill
Q: I own an '81 Corvette that has a slow air-conditioning leak. For years I just recharged the system in the spring and hoped it would cool until fall. That didn't work for me this year, so I've decided to convert the system to R-134a, rather than continue to pay $35 per pound for R-12. I would like to do this over the winter, when I don't drive the car as much.
From what I understand, the recommended retrofit procedure consists of simply evacuating the system, repairing the leak(s), adding service-port adapters, charging the system with R-134a and PAG oil, and running it as is. The final is step is to pull a vacuum on the system for 30-45 minutes to boil out any remaining moisture and air. (I know there are other methods, but I'm trying to stay with the most economical.)
My question is, when recharging the system, is there a conversion chart or formula that will tell me how much R-134a to use? Or do I use the same amount of R-134a as I would R-12?
A: The sticker on your car probably calls for 3.0 pounds of R-12. If so, the system should take 2.45 pounds of R-134a. When converting from R-12 to R-134a, multiply the given R-12 amount by 0.9 and then subtract 0.25 from that amount to get the R-134a number.
Why? R-134a has a higher pressure than R-12 at a given temperature. Therefore, you must use less R-134a in your system than you would R-12.
When performing an inexpensive conversion, I would also recommend that you remove the compressor, drain out as much mineral oil as possible, and replace it with PAG (polyalkylene glycol) oil. You also may need to adjust the clutch-cycling switch on some A/C systems.
Knock, Knock: No Joke
Q: I'm the owner of a stock '99 Corvette with 65,000 miles and an automatic transmission. I've had the car for several years now and have experienced no mechanical difficulties during that time. I only use the recommended synthetic oil, and I only drive the car during the warm months here in Ohio (May through October).
Recently, the engine developed a knock. (I'm an old gearhead from the '60s, so I know a little about engines.) It sounds like a lifter to me, but here's the odd part: When I first start the car and the engine is cold, I don't hear it. But when I back out of my driveway and add gas, the knocking becomes very prevalent. It then goes away as soon as the transmission shifts into Second gear.
When I reach the end of the block, stop, and then pull away again, there is no knock in First or any other gear. Similarly, if I let the car sit at idle and warm up to full operating temperature before driving, the knock does not occur. (I should note that the car runs great whether it knocks or not.)
My mechanic did some research and tells me that it could be a worn cam lobe. He also suggested that the synthetic oil GM requires in these cars has changed over the years, and that some of the cam-protecting additives have been removed. I'm having a hard time buying into this, but he is a mechanic I know and trust.
I would appreciate your thoughts as to why an engine with only 65,000 miles might have a worn cam. Do you have any other ideas about what might be causing the knock?
A: While it's impossible to know for sure without hearing your car's engine in person, it's unlikely that the problem is attributable to a worn cam lobe. Your mechanic is correct in that some oil formulations have changed in recent years, but this should have no bearing on your situation, which involves a synthetic lubricant and a hydraulic-roller valvetrain. (For more information on oil additives, see our "All About Oil" article elsewhere in this issue.)
A far more common problem with LS1 engines is piston slap, which is caused by excessive piston-to-bore clearance during cold operation. The good news is that this isn't a harmful sort of noise. Chevrolet has acknowledged the issue and states that while there is no fix, it will not affect the engine's performance or life expectancy.