P1632

Code

CADILLAC P — Powertrain

Theft Deterrent System Fuel Disabled

Brand: CADILLAC

Type: P — Powertrain

Views: UK: 45 EN: 112 RU: 104

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Page language: EN

Causes

Immobilizer/anti-theft module commanded fuel disable
Invalid or unrecognized key/transponder
Faulty body control module (BCM) or theft deterrent module
Loss of CAN/serial communications between security and engine/fuel modules
Blown fuse or failed relay in fuel/anti-theft circuit
Damaged wiring or poor ground in security/fuel circuits

Symptoms

Engine cranks but will not start (no fuel)
No fuel pump priming when ignition ON
Security/anti-theft indicator illuminated or flashing
MIL may be on with multiple related security or communication codes
Random no-starts or intermittent start failures

What to check

Verify immediate symptom: does fuel pump prime with key ON?
Check theft/SECURITY indicator behavior at key ON and during crank
Scan for all DTCs in BCM, ECM/PCM, theft module and other modules
Check fuses and relays related to fuel pump and security system
Verify battery voltage (low voltage can trigger security faults)
Inspect key and spare key for damage; try all known good keys

Signal parameters

Security indicator lamp status (on/flash pattern)
Fuel pump relay control (coil activation signal)
Fuel pump voltage at relay and at pump while cranking
CAN/serial messages between BCM/theft module and ECM (status codes)
Immobilizer authorization bit/state from theft module to ECM
Transponder/key ID read by theft antenna module

Diagnostic algorithm

Retrieve and record all stored DTCs and freeze frame data from all modules (BCM, ECM/PCM, theft module).
Observe and note behavior of SECURITY lamp with key ON/crank. Compare to correct pattern in service manual.
Attempt start while monitoring fuel pump operation and fuel system voltage. If pump does not run, verify fuel pump fuse and relay operation.
Check for communication errors on CAN/serial network. Use scan tool to confirm theft module and ECM are communicating and share the same VIN/key authorization state.
Inspect wiring and connectors for the theft module, BCM, and fuel pump relay for corrosion, damage, or poor grounds.
Verify key transponder recognition: try all vehicle keys and a known good spare. If only certain keys fail, suspect key/transponder or key programming.
Check battery voltage and charge if low; then clear codes and attempt re-learn/start procedures per service manual (some GM/Cadillac systems require key relearn after battery disconnect).
If module communications or authorization failures persist, follow module-specific diagnostics: test theft module power/ground, test antenna module/readers, check immobilizer input/output signals with a scope or data log.
If a module is found defective or was replaced, ensure correct programming and VIN/key coding using OEM scan tool before retesting.
After repairs, clear codes and verify vehicle starts reliably and that the security indicator behaves normally. Re-scan for recurrence.

Likely causes

Faulty key/transponder not recognized by the Passlock/immobilizer
BCM or theft deterrent module internal fault
Security module lost VIN/key coding after battery disconnect or module replacement
Fuel pump relay or fuel pump disable circuit open due to damaged wiring or blown fuse
Intermittent CAN bus error between theft module and ECM/PCM

Fault status

⚠️ Status

The vehicle's theft deterrent system has disabled fuel delivery or refuses to authorize the fuel system. Engine start is prevented until the immobilizer/security authorization is restored or the underlying fault is repaired.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-2.5 hours

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Repair manuals

Manual library for CADILLAC

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Browse 206 CADILLAC manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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P1632 — Theft Deterrent System Fuel Disabled