P1690 — Fuel Injection Pump CKP Sensor Does Not Agree With ECM CKP Sensor — 5.9 Cummins 24-Valve (VP44)

Diagnostic reference for 5.9 Cummins 24-Valve VP44 (1998.5-2002) when P1690 is set. Focus on signal disagreement between the VP44 internal speed signal and the…

Updated October 15, 2026

What it means

Manufacturer-enhanced code: the VP44’s internal speed signal disagrees with the engine crankshaft position signal.¹

Most likely causes

1. Crankshaft position sensor signal degraded or intermittent — Erratic or out-of-range CKP signal can cause the ECM CKP reading to diverge from the VP44 internal speed signal.¹²
2. VP44 pump-mounted controller internal fault — A failing VP44 controller can produce an incorrect internal speed signal that no longer matches the ECM CKP.¹
3. VP44 electrical connector, power or ground issue — Poor VP44 connector contact, corrosion, or weak power/ground raises noise or dropouts in the pump’s speed reporting.¹
4. ECM-to-pump wiring or data link degradation — Intermittent wiring between ECM and VP44 can corrupt the speed comparison and set the disagreement code.¹³
5. Companion DTC present in another module — P1693 can accompany P1690 when another module stores a related fault; the companion code points to the real issue.⁴
6. Lift-pump fuel starvation stressing VP44 electronics — Chronic low supply pressure stresses the VP44 controller and can contribute to erratic pump signals.⁵⁶

How to diagnose

1. Verify code presence and freeze-frame conditions; record engine speed, temperature, and load at set.
2. Inspect crankshaft position sensor and wiring for damage, oil contamination, and secure mounting; check air gap and connector integrity.
3. Inspect VP44 pump connector, terminals, and harness for corrosion, moisture, or loose pins; verify pump power and ground circuits for proper voltage and low resistance.
4. Check ECM-to-pump data wiring continuity and isolation to ground and power; look for chafing near the engine and firewall.
5. Monitor live CKP RPM vs VP44 reported speed with a scan tool during cranking and idle; note dropouts or divergence.
6. Check lift-pump supply pressure at the injection pump inlet per service spec; low pressure is a known VP44 stressor.
7. Read all modules for additional codes, especially P1693 companion codes, P1688, P1689, P0251, and CKP circuit codes.
8. If electrical checks pass and signal disagreement persists, evaluate VP44 controller health; a failing pump controller can set this disagreement.
9. Document findings before condemning the VP44; replace only after confirming power, ground, wiring, CKP signal, and fuel supply are correct.

Specs and test values

Common mistake to avoid

Replacing the VP44 without testing the lift pump first. A weak lift pump starves the VP44 of the fuel it uses for cooling, so a new pump installed on a bad supply side can fail again quickly. Put a gauge on the feed line and check pressure at key-on and under load before buying the pump. Source: Diesel Power Products — checking lift pump pressure on a 24-valve Cummins.

Parts and tools you may need

• Digital multimeter
• Scan tool with live data for CKP RPM and VP44 speed
• Wiring diagram for 1998.5-2002 5.9L 24-valve
• Terminal cleaner and dielectric grease
• Fuel pressure gauge for lift-pump supply test

Tools you’ll need

• OBD-II scan tool — Reads P1690 and companion codes and compares live CKP RPM vs VP44 reported speed to confirm signal disagreement.
• digital multimeter — Checks VP44 power, ground, and ECM-to-pump data wiring for correct voltage, resistance, and isolation to ground.
• fuel pressure gauge — Verifies lift-pump supply pressure at the VP44 inlet to rule out fuel starvation stressing the pump electronics.
• oscilloscope — Captures CKP sensor waveform integrity and VP44 speed signal to detect dropouts or noise causing disagreement.

Rough cost and difficulty

Typical US independent-shop figures; labor runs about $120–$180 per hour (dealers charge more). Confirm the diagnosis before buying parts.

When to see a pro

If diagnosis points to internal VP44 controller failure or requires pump removal, have a qualified diesel technician perform the work. Do not attempt high-pressure fuel system service without proper training and safety equipment.

Check for recalls

Recalls are tied to your truck’s VIN, so check yours directly: enter the VIN at NHTSA’s recall lookup. Open safety recalls are repaired free at a dealer.

Sources