SYS.OK|MANUAL.DB● LIVE
HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 83 (ENGINE CONTROLS - SELF-DIAGNOSTICS)DIAGNOSTIC TESTSDTC P0340: CAMSHAFT POSITION SENSOR CIRCUITDESCRIPTION
1999 GMC Forward Control 5.7 R, Automatic

DTC P0340: Camshaft Position Sensor Circuit: Description

1999 GMC Forward Control 5.7 R, AutomaticSECTION Description
WARNING: This page is about a different car, the 2002 Saturn LW200, 2002 Saturn L200, and 2002 Saturn L100. However, it is still accessible from the selected car via links, so may be relevant.

Electronic Ignition (EI) module supplies 5 volts to cam signal circuit whenever it determines cylinder No. 1 or cylinder No. 3 has just fired on its compression stroke. EI module uses capacitive pick-up plates located under 1/4 and 2/3 coil packs to determine polarity sequence and voltage amplitude of cylinder 1/4 and 2/3 secondary ignition. PCM has an internal resistor tied to ground on signal line in order to detect zero volts when no cam signal is received. Since engine firing order is 3-4-2-1, PCM expects to see a bit pattern of 00000110 or 00001001 after firing order is complete (only last 4 bits are used). A "1" bit equals 5 volts and a "0" bit equals zero volt. This bit pattern can be read on scan tool as CALC. COMPRESSION OUTPUT. If bit pattern 00000110 is detected, PCM is syncing engine on TDC compression cylinder No. 2. If bit pattern 00001001 is detected, PCM is syncing engine on TDC compression cylinder No. 3. DTC sets when PCM detects no change in cam signal input for a certain number of engine revolutions during engine crank or initial start.

RENDER: 1.0x

NO RELATED

Recommended Tools & Savings

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Affiliate disclosure: We may earn a commission at no extra cost to you.

Shop Manual-Ready ToolsFree Quote CheckQuote Shield Pro

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.