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Jerry Newton
Jerry Newton, GMC Technician
Category: GM
Satisfied Customers: 4750
Experience:  ASE Master Technician, L1, Master GM Technician. Over 20 years of bumper to bumper GM experience.
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2008 GMC Savana 1500 - 4.3 - No power - Limp mode - Was very

Customer Question

2008 GMC Savana 1500 - 4.3 - No power - Limp mode - Was very low on oil and now throws codes: P0016, P0128, P0300, P0340, P0341, P0573, P0641 and P1133. (Please don't respond to this question with the description of the codes - I know what they are). Thinking problem with VVT but don't know where to start. Have filled with oil but still no power.
Submitted: 2 years ago.
Category: GM
Expert:  Jerry Newton replied 2 years ago.
The camshaft position seems to be the big issue here. There are other codes, of course, but the CMP is the biggest hint in the trouble codes. Known problems are with the CMP and wiring, the wiring can get melted on the exhaust manifold or otherwise damaged in the harness. Put your eyes and hands on the wiring and just trace it up to the top of the engine, to see if it's chafed or damaged anywhere. It's not necessarily a problem with the VVT if you're getting P0340 and P0341... the computer is pretty savvy and can usually tell the difference between a cam that's not advancing/retarding correctly, and a signal that just doesn't make any sense at all.
Customer: replied 2 years ago.

Checked wiring - no problems found. Replaced sensor (which was a real pain as it was stuck in the front cover - had to take it out in pieces). After replacing sensor and clearing codes P0340 came right back on startup (hard code) and van went into limp.

Expert:  Jerry Newton replied 2 years ago.
When you say you "checked wiring" how did you check it? Visually, of course, but did you put an ohmmeter to it to test for continuity and short to ground? I can give you a schematic for this, if you need it.
Customer: replied 2 years ago.

Visually checked connector and harness, especially near manifold. No signs of damage. No short to ground. Has 5v reference.

Expert:  Jerry Newton replied 2 years ago.
This code tells us specifically that the computer is not receiving CMP signal. So, if you have 5v reference and ground, the CMP sensor should be creating a signal every time the high spot on the cam gear comes around. I would physically check and make sure that the high spot on the cam gear is visible as the engine goes around. If it is, then there isn't a mechanical issue. I would then have a lab scope on these wires to see if there is a signal being produced. If there is, then your PCM is not seeing it, and is therefore faulty. If not, then there is a wiring issue or a sensor issue that needs to be addressed. Lab scope is a pretty useful tool, most high end repair shops have them these days, my own shop included. The ability to "see" what the computer sees is critical when making a diagnosis like this.