P1345 Code on a GMC: Crankshaft–Camshaft Position Correlation (GMC Guide)

P1345 is a GM-specific code, and on a GMC it means one of two quite different things depending on the engine. On a late-1990s Sierra, Savana, Safari, Jimmy, Sonoma, Yukon or Suburban with a Vortec 4.3L, 5.0L, 5.7L or 7.4L distributor engine, GM's own tables call it "Camshaft Sensor Misinstalled" — a check of whether the cam sensor inside the distributor, and the distributor itself, were installed in the right position. On a 2002–2003 Envoy with the 4.2L inline six, the same number is GM's "VCP Crank/Cam Correlation Error", the job P0016 took over from 2004. The surprise on the Vortec trucks is that turning the distributor does not change spark timing at all — which is exactly why so many P1345s appear the day after someone "set the timing."

What Does P1345 Mean on a GMC?

Every GMC engine that sets P1345 compares two signals: the crankshaft position sensor, which the computer uses to fire the plugs and time injection, and a camshaft position signal, which tells it which stroke each cylinder is on. P1345 sets when the cam signal does not arrive where the computer expects it relative to the crank.

What GM is checking differs by engine:

• Vortec distributor engines (1997–2002 tables). GM's OBD tables for the 4.3L (L35, LF6), 5.0L (L30), 5.7L (L31) and 7.4L (L29) describe P1345 as "Camshaft Sensor Misinstalled — 1X signal. This diagnostic will determine if the Cam sensor and high voltage switch have been installed correctly." It fails when the cam signal's falling edge is out of phase with the crank signal's falling edge by more than ±26 degrees on the 1997–2000 4.3L, 5.0L and 5.7L tables, ±15 degrees on the 2000 7.4L table, and ±27 degrees on the 2001–2002 combined truck tables — 30 failures within a 50-test sample. The 1997–2000 tables list it as a Type A code (light on the first failure); the 2001–2002 tables list it as Type B.
• 4.2L LL8 (2002–2003 tables). GM's tables for the Envoy's inline six call P1345 "VCP Crank/Cam Correlation Error — detects out of range base engine cam timing." With the cam phaser commanded to 0 for 16 seconds, it fails when crank degrees compared with cam degrees are above 74.7 or below 56.7, counted as 10 of 20. It is a Type B code.

Because it is a manufacturer code, a very basic reader may show P1345 with no description. A scan tool with GM-enhanced data reads it properly and, on the Vortec trucks, shows the Cam Retard Offset value you need to fix it.

Which GMCs Set P1345

GM's tables list P1345 for the engines below. The GMC models are the ones that used them:

• 4.3L V6 (L35, LF6, LU3): Sierra C/K pickups, Savana, Safari, Jimmy and Sonoma.
• 5.0L V8 (L30) and 5.7L V8 (L31): Sierra C/K pickups, Yukon and Suburban of the period, and Savana vans.
• 7.4L V8 (L29): heavier C/K and Suburban applications through 2000.
• 4.2L inline six (LL8): 2002–2003 Envoy and Envoy XL.

We read GM's tables for 1997, 1998, 1999, 2000, 2001 and 2002 Vortec trucks; all list P1345. Our copies of the 1996 tables did not extract readable text, so we cannot confirm 1996 from GM. GM's 2003 table for the 4.3L and light-duty truck V8s does not list P1345, and we could not confirm what a 2003-and-later distributor 4.3L reports instead. On the LL8, GM's 2004 table lists P0016 in place of P1345 — see our P0016 GMC guide for 2004-on Envoys.

The 1999-and-later Sierra and Yukon with the Gen III 4.8L, 5.3L and 6.0L have no distributor. GM's 2002 table marks P1345 as not required on the 5.3L LM7, and P1345 on those engines is not the distributor story below. GM's Duramax LB7 tables also reference P1345 — diesels follow their own diagnostics and are not covered here.

The Vortec Distributor Trucks

On a pre-1996 small block, you loosened the distributor and turned it to set timing with a light. On a 1996-and-later Vortec, that habit causes problems. Spark timing comes from the crankshaft sensor behind the balancer. The distributor still routes spark through the cap and rotor and still carries the cam sensor, but turning it does not advance or retard the spark.

What turning it does change:

• Rotor phasing — where the rotor tip sits against each cap terminal when the coil fires. Far enough out and the spark can jump to the wrong terminal, causing crossfire and misfires.
• Cam sensor position — the signal GM's P1345 test watches. That is exactly why GM named the code "Camshaft Sensor Misinstalled."

So P1345 on a Sierra, Savana or Safari is, first of all, a question: has anyone had the distributor out or turned it? Intake gasket jobs on these engines often involve pulling the distributor, and a replacement distributor dropped in a tooth off, or a gear that doesn't seat, will set the code too.

Cam Retard Offset

On the Vortec trucks, the value that tells you whether the distributor is indexed correctly is Cam Retard Offset on a GM-capable scan tool. The procedure quoted by technicians from the factory service manual is:

1. Bring the engine to full operating temperature.
2. Hold engine speed at at least 1,000 rpm.
3. Read Cam Retard Offset. The target circulated is 0°, plus or minus 2°.
4. If it reads negative, rotate the distributor counterclockwise; if positive, clockwise. Move it in small steps.
5. Tighten the hold-down to the service manual torque and recheck.

We are passing this procedure on secondhand: it is widely quoted from GM's manual, but we could not open the GM document itself, and the hold-down torque that circulates with it is inconsistent between sources. Use your service manual's figure. What we can confirm from GM's own tables is the fault threshold — the code sets far outside that ±2° target, at about ±26° (±27° on 2001–2002, ±15° on the 2000 7.4L). A truck with a reading a few degrees out may run fine without a code; one far enough out to set P1345 is badly indexed or has a mechanical problem.

A reading that will not settle is a different problem from one that is steady but off. Steady and off means indexing. Jumping several degrees with the engine steady means wear in the distributor shaft or gear, a loose rotor, a failing sensor, or a timing chain with slack.

The 2002–2003 Envoy 4.2L

On the Envoy's LL8, P1345 is a cam phaser–era correlation code. GM's test commands the exhaust-cam phaser to its zero position and checks base cam timing against the crank — so it catches a chain that has jumped or stretched, a cam timed wrong after engine work, or a phaser that will not return to zero.

NHTSA's index lists three GM documents for the 2002–2004 Envoy and Envoy XL that name "P0016 or P1345":

• 01623 — 4.2L LL8 DTC P0016 or P1345 with no driveability symptoms.
• 00156A — 4.2L LL8 rough idle/run, possible P1345 or P0016.
• 3659A — service engine soon light after internal engine repairs due to P0016 or P1345.

We have seen only NHTSA's one-line summaries; the documents themselves are not in the archive. GM's later inline-engine documents fill in the picture: PIP3694F (2004–2011 Envoy) points at missing cam actuator solenoid screens and crankshaft end play for P0014/P0017, and PIP4945B (2004–2009 Envoy) lists timing errors, a loose crank gear and oil problems for P0017. Those are later codes, not P1345, but they are the same engine and the same family of causes.

Symptoms of P1345

• Check engine light, often with no other complaint if the error is modest
• Misfire, stumble or rough running under load from crossfire if rotor phasing is far out (Vortec)
• Hard starting
• The code appearing right after an intake, distributor or engine job
• Rough idle on a 2002–2003 Envoy (GM index entry 00156A)
• P0335 or P0340 stored alongside when a sensor or its wiring is failing

Causes and How to Confirm Each

How Is P1345 Diagnosed on a GMC?

1. Identify the engine. A distributor Vortec and a 4.2L Envoy follow different paths.
2. Read the code with a GM-capable tool that shows Cam Retard Offset (Vortec) or cam position data (LL8).
3. Ask what work has been done. Distributor, intake or engine work points straight at indexing or timing.
4. Vortec: warm the engine, hold 1,000 rpm or more and read Cam Retard Offset. Steady and off means re-index; wandering means inspect the distributor first.
5. Check for P0335 or P0340 and test sensors and wiring if they are present.
6. Envoy: check oil level and condition, then cam timing against the crank per service information.
7. Adjust or repair, then recheck the reading before clearing the code.
8. Road test under load to confirm the misfire or stumble is gone.

Parts and Cost

GM Documents for P1345 on GMC Models

No GM service bulletin we found names P1345 on a GMC Vortec truck. The GM documents that define the code for GMC engines are GM's own OBD tables, plus three Envoy index entries.

Have a dealer check your VIN against current bulletins rather than relying on any article, including this one. The check is free, even on an older truck.

What Other P1345 Pages Get Wrong

• "Adjust ignition timing by turning the distributor." On a Vortec, timing comes from the crank sensor. Turning the distributor changes rotor phasing and the cam signal — which is what sets P1345.
• "The target is the same as the code limit." GM's tables set the code at roughly ±26°; the indexing target technicians quote is 0° ±2°. A truck can be well off target without a code.
• "P1345 only exists on distributor engines." On a 2002–2003 Envoy, P1345 is the 4.2L's cam-to-crank correlation code.
• "Replace the cam sensor first." GM's own name for the Vortec code is "Camshaft Sensor Misinstalled" — position, not failure, is the usual problem.
• Applying it to modern GMCs. Later Sierras, Yukons and Envoys report cam-to-crank correlation as P0016–P0019. For the Chevrolet side of the Vortec story, see our P1345 Vortec guide for Chevrolet.

Frequently Asked Questions

What does P1345 mean on a GMC Sierra with a 5.7L?

GM's tables call it "Camshaft Sensor Misinstalled": the cam signal from the distributor is too far out of phase with the crank signal. It almost always means the distributor is indexed wrong or worn.

Will re-indexing the distributor change my timing?

No. On a Vortec, spark timing comes from the crankshaft sensor. Re-indexing corrects rotor phasing and the cam signal.

Why did P1345 appear after my intake gasket job?

Because the distributor usually comes out for that job. If it goes back in a tooth off or turned, the cam signal is out of phase. Re-index it using Cam Retard Offset.

Does a 2003 Envoy use P1345?

Yes. GM's 2002 and 2003 tables for the 4.2L LL8 list P1345 as the cam/crank correlation error. GM's 2004 table lists P0016 instead.

Is P1345 serious?

Usually not dangerous, but don't ignore it. On a Vortec, a badly indexed distributor can crossfire and misfire; on an Envoy, it can mean cam timing is off. Either can get worse with time.

Can a basic code reader show P1345?

It may show the number with no description. A GM-capable scan tool reads it properly and shows the Cam Retard Offset value you need.