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Home / DTC / P0512 — Starter Request Circuit

P0512 — Starter Request Circuit

Detailed page for trouble code P0512.

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22,491specific
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Code

P0512

Generic P — Powertrain

Starter Request Circuit

Brand: Generic
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Open or short in starter request wiring
  • Failed starter relay or relay socket
  • Faulty ignition switch or key switch contacts
  • Poor connector contact or corrosion at relay, starter solenoid or module
  • Weak or discharged battery or poor battery terminals/ground
  • Intermittent wiring damage (chafing, pinched, broken strands)

Symptoms

  • No-crank (key to START produces no starter action)
  • Intermittent crank/no-crank condition
  • Starter engages without key or unexpected cranking (rare)
  • No change in starter request signal when turning key
  • Possible illuminated MIL or security lamp

What to check

  • Scan for stored/active codes and freeze-frame data; note key status and battery voltage
  • Measure battery resting and cranking voltage; verify good battery terminals and ground
  • Visually inspect fuses, fusible links and starter relay; swap known-good relay if available
  • Inspect starter, solenoid and relay connectors for corrosion, heat damage, loose pins
  • Backprobe starter request wire at relay/PCM while actuating START; observe voltage behavior
  • Wiggle test wiring harness while cranking to reproduce intermittent failures

Signal parameters

  • Rest (no start): starter request circuit ≈ 0 V (or low) relative to battery negative
  • Cranking (key START): starter request circuit ≈ battery voltage (~9–14 V) when driver requests starter
  • Intermittent signal: erratic/noisy voltage, rapid drop under load, or pulsed output
  • Continuity: low resistance path between ignition switch, relay coil, and PCM/BCM input when measured per service manual

Diagnostic algorithm

  1. Retrieve codes and live data; note battery voltage and starter request status during attempt to start.
  2. Verify battery condition and clean/tighten battery terminals and main grounds. Re-check code after restoring proper battery connections.
  3. Inspect relevant fuses, fusible links and the starter relay. Swap relay with identical known-good relay to quickly test.
  4. Backprobe the starter request/command wire at the relay coil or PCM input. With helper turning key to START, observe voltage and behavior. Expect ~battery voltage during crank, ~0 V otherwise.
  5. If request voltage is absent, trace wiring back to ignition switch and PCM. Check for opens/shorts to power or ground and poor connector pins. Repair or replace damaged wiring/connectors.
  6. If request voltage is present at relay but starter does not operate, check relay output to starter solenoid and measure voltage at starter solenoid terminal during crank. If voltage present but starter does not engage, investigate starter/solenoid.
  7. If intermittent signal or noisy voltage is found, perform wiggle tests along harness and repair wiring harness chafe or broken wires.
  8. If wiring and starter/relay check good, test or substitute PCM/BCM driver per manufacturer procedures; check immobilizer module/antitheft inhibit circuits and key programming as applicable.
  9. After repairs, clear codes, perform multiple start attempts and road test to confirm repair. Re-scan for codes and monitor live data.

Likely causes

  • Corroded/loose connector at starter relay or starter solenoid
  • Open wire between ignition switch and starter relay/PCM
  • Stuck or failed starter relay coil
  • Low battery voltage causing erroneous signal
  • Ground loss at starter or chassis ground strap

Fault status

⚠️ Status
Starter Request Circuit fault — open, short, intermittent or out-of-range voltage detected on the starter request/command circuit. Inspect wiring, relay, ignition switch, battery and control module.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

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Code

P0512

HUMMER P — Powertrain

Start Switch Circuit

Brand: HUMMER
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Open or short in starter request wiring
  • Failed starter relay or relay socket
  • Faulty ignition switch or key switch contacts
  • Poor connector contact or corrosion at relay, starter solenoid or module
  • Weak or discharged battery or poor battery terminals/ground
  • Intermittent wiring damage (chafing, pinched, broken strands)

Symptoms

  • No-crank (key to START produces no starter action)
  • Intermittent crank/no-crank condition
  • Starter engages without key or unexpected cranking (rare)
  • No change in starter request signal when turning key
  • Possible illuminated MIL or security lamp

What to check

  • Scan for stored/active codes and freeze-frame data; note key status and battery voltage
  • Measure battery resting and cranking voltage; verify good battery terminals and ground
  • Visually inspect fuses, fusible links and starter relay; swap known-good relay if available
  • Inspect starter, solenoid and relay connectors for corrosion, heat damage, loose pins
  • Backprobe starter request wire at relay/PCM while actuating START; observe voltage behavior
  • Wiggle test wiring harness while cranking to reproduce intermittent failures

Signal parameters

  • Rest (no start): starter request circuit ≈ 0 V (or low) relative to battery negative
  • Cranking (key START): starter request circuit ≈ battery voltage (~9–14 V) when driver requests starter
  • Intermittent signal: erratic/noisy voltage, rapid drop under load, or pulsed output
  • Continuity: low resistance path between ignition switch, relay coil, and PCM/BCM input when measured per service manual

Diagnostic algorithm

  1. Retrieve codes and live data; note battery voltage and starter request status during attempt to start.
  2. Verify battery condition and clean/tighten battery terminals and main grounds. Re-check code after restoring proper battery connections.
  3. Inspect relevant fuses, fusible links and the starter relay. Swap relay with identical known-good relay to quickly test.
  4. Backprobe the starter request/command wire at the relay coil or PCM input. With helper turning key to START, observe voltage and behavior. Expect ~battery voltage during crank, ~0 V otherwise.
  5. If request voltage is absent, trace wiring back to ignition switch and PCM. Check for opens/shorts to power or ground and poor connector pins. Repair or replace damaged wiring/connectors.
  6. If request voltage is present at relay but starter does not operate, check relay output to starter solenoid and measure voltage at starter solenoid terminal during crank. If voltage present but starter does not engage, investigate starter/solenoid.
  7. If intermittent signal or noisy voltage is found, perform wiggle tests along harness and repair wiring harness chafe or broken wires.
  8. If wiring and starter/relay check good, test or substitute PCM/BCM driver per manufacturer procedures; check immobilizer module/antitheft inhibit circuits and key programming as applicable.
  9. After repairs, clear codes, perform multiple start attempts and road test to confirm repair. Re-scan for codes and monitor live data.

Likely causes

  • Corroded/loose connector at starter relay or starter solenoid
  • Open wire between ignition switch and starter relay/PCM
  • Stuck or failed starter relay coil
  • Low battery voltage causing erroneous signal
  • Ground loss at starter or chassis ground strap

Fault status

⚠️ Status
Starter Request Circuit fault — open, short, intermittent or out-of-range voltage detected on the starter request/command circuit. Inspect wiring, relay, ignition switch, battery and control module.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

P0615 P0638 P0627
Repair manuals

Manual library for HUMMER

138

Browse 138 HUMMER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

HUMMER

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Code

P0512

LAND ROVER P — Powertrain

Slow start request circuit Starter request circuit immobilizer Incorrect immobilizer key battery electrolyte

Brand: LAND ROVER
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Open or short in starter request wiring
  • Failed starter relay or relay socket
  • Faulty ignition switch or key switch contacts
  • Poor connector contact or corrosion at relay, starter solenoid or module
  • Weak or discharged battery or poor battery terminals/ground
  • Intermittent wiring damage (chafing, pinched, broken strands)

Symptoms

  • No-crank (key to START produces no starter action)
  • Intermittent crank/no-crank condition
  • Starter engages without key or unexpected cranking (rare)
  • No change in starter request signal when turning key
  • Possible illuminated MIL or security lamp

What to check

  • Scan for stored/active codes and freeze-frame data; note key status and battery voltage
  • Measure battery resting and cranking voltage; verify good battery terminals and ground
  • Visually inspect fuses, fusible links and starter relay; swap known-good relay if available
  • Inspect starter, solenoid and relay connectors for corrosion, heat damage, loose pins
  • Backprobe starter request wire at relay/PCM while actuating START; observe voltage behavior
  • Wiggle test wiring harness while cranking to reproduce intermittent failures

Signal parameters

  • Rest (no start): starter request circuit ≈ 0 V (or low) relative to battery negative
  • Cranking (key START): starter request circuit ≈ battery voltage (~9–14 V) when driver requests starter
  • Intermittent signal: erratic/noisy voltage, rapid drop under load, or pulsed output
  • Continuity: low resistance path between ignition switch, relay coil, and PCM/BCM input when measured per service manual

Diagnostic algorithm

  1. Retrieve codes and live data; note battery voltage and starter request status during attempt to start.
  2. Verify battery condition and clean/tighten battery terminals and main grounds. Re-check code after restoring proper battery connections.
  3. Inspect relevant fuses, fusible links and the starter relay. Swap relay with identical known-good relay to quickly test.
  4. Backprobe the starter request/command wire at the relay coil or PCM input. With helper turning key to START, observe voltage and behavior. Expect ~battery voltage during crank, ~0 V otherwise.
  5. If request voltage is absent, trace wiring back to ignition switch and PCM. Check for opens/shorts to power or ground and poor connector pins. Repair or replace damaged wiring/connectors.
  6. If request voltage is present at relay but starter does not operate, check relay output to starter solenoid and measure voltage at starter solenoid terminal during crank. If voltage present but starter does not engage, investigate starter/solenoid.
  7. If intermittent signal or noisy voltage is found, perform wiggle tests along harness and repair wiring harness chafe or broken wires.
  8. If wiring and starter/relay check good, test or substitute PCM/BCM driver per manufacturer procedures; check immobilizer module/antitheft inhibit circuits and key programming as applicable.
  9. After repairs, clear codes, perform multiple start attempts and road test to confirm repair. Re-scan for codes and monitor live data.

Likely causes

  • Corroded/loose connector at starter relay or starter solenoid
  • Open wire between ignition switch and starter relay/PCM
  • Stuck or failed starter relay coil
  • Low battery voltage causing erroneous signal
  • Ground loss at starter or chassis ground strap

Fault status

⚠️ Status
Starter Request Circuit fault — open, short, intermittent or out-of-range voltage detected on the starter request/command circuit. Inspect wiring, relay, ignition switch, battery and control module.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

P0615 P0638 P0627
306

Browse 306 LAND ROVER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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+100 karma for a short comment :)
Keep it short and practical. Up to 500 characters.
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