← Back to list

1997 GMC Safari Intake Gasket Replacement Leads to P0340 Code - Troubleshooting Guide

Model: 1997 GMC Safari Fault Code: P0340 Posted: 2007-06-17 09:46

Hi everyone, I'm seeking help with a recurring issue on my 1997 GMC Safari Conversion Van. After purchasing the vehicle, I discovered a blown intake gasket that was causing coolant to leak from the driver's side front of the intake. The car started fine initially and ran well despite the leak. I replaced the intake gasket and cleaned both the upper plenum and lower intake, which improved engine performance significantly. After reinstalling the 'dog house' cover (the hood-style accessory panel), I began experiencing several problems: no temperature gauge reading, a persistent check engine light, and difficulty starting the engine. Upon inspection, I realized that during installation of the dog house cover, I had accidentally disconnected the temperature sensor wiring at the back of the engine. Reconnecting this wire restored the temperature gauge, but the check engine light remained on and hard starts persisted. I scanned the system and found a P1345 code indicating a CMP/CHK (Cam Position / Crankshaft Position) sensor correlation issue. I suspected that the missing temperature reading might have caused misalignment in sensor data, so I cleared the codes — but the problem returned. I then replaced both the camshaft position sensor, distributor cap, and rotor, performed a visual inspection of all connectors and components, and still saw no improvement. After these efforts, the engine started better temporarily, but the check engine light reappeared with a new code: P0340 — indicating an issue with the camshaft circuitry. The camshaft only has two possible installation orientations, so I'm confident it's not misaligned. However, I'm at a loss as to what else could be causing this. I'm looking for clear guidance on how to diagnose and resolve this P0340 code in a 1997 GMC Safari with a distributor-based ignition system. Any insights or step-by-step troubleshooting tips would be greatly appreciated.

Related fault codes
P0340
Comments (10)
Anonymous 2007-06-17 18:26

The camshaft gear does not have only two installation positions — that's a common misconception. While the oil pump shaft doesn't require precise alignment, the cam gear must be installed correctly and properly adjusted (some models lack adjustment capability). A misalignment here is a frequent cause of P0340 codes. In many cases, when an intake gasket is replaced and a P0340 code appears, it's due to the distributor being installed one tooth out of alignment with the camshaft.

Anonymous 2007-06-18 05:14

I've tried adjusting the distributor by moving it just one tooth — but when I do that, it doesn't seat fully. I recall reading that a distributor only fits correctly or at exactly 180 degrees out. Is this referring to the oil pump shaft? If so, is there any way to adjust that shaft? You're right — once the distributor is locked in place, it can't be moved. Your explanation makes perfect sense. I've now checked TDC on cylinder #1 and believe it's off by one tooth. I just don't know how to correct this properly.

Anonymous 2007-06-18 06:18

Turn the oil pump drive shaft with a long screwdriver to adjust the distributor position before final installation.

Anonymous 2007-06-18 06:29

I'm not feeling very confident right now. I never thought about adjusting the oil pump shaft — it's been such a frustrating experience trying to fix this myself, assuming it was purely an electrical issue. Thanks for the helpful insight.

Anonymous 2007-06-18 09:13

My personal recommendation is to install the distributor correctly from the start and avoid overcomplicating alignment. To ensure proper seating, turn the engine by hand while applying gentle pressure on the distributor. As you rotate the engine, the distributor will drop into place when it engages with the oil pump shaft.

Anonymous 2007-06-18 09:36

Different approaches here — I've seen more than one person install the distributor off by a tooth using that method! On a Safari with the head under the dash, someone might have a good view down there, but I suspect not everyone has that advantage.

Anonymous 2007-06-18 09:41

I used to rely on that hand-tightening technique, but after years of frustration from misalignments, I now prefer this method — it's faster and more reliable. It works well for me personally, though it may not suit everyone. It requires a bit more skill.

Anonymous 2007-06-18 10:25

That’s why I suggested the simpler method for him! He’s already frustrated — if he gets the camshaft in the right position, I’d rather he adjust the distributor via the oil pump shaft than try to force it into place by hand. It's a valuable learning experience and worked perfectly for me!

Anonymous 2007-06-18 12:04

Yeah, you're absolutely right.

Anonymous 2007-06-19 09:14

Thanks everyone! I finally adjusted the distributor by turning the oil pump shaft, and now everything is working perfectly — no check engine light, smooth starts, and normal temperature readings. This was a real relief!