Fix P0652: Mechanic’s solutions that WORKED

The P0652 code signifies a low voltage problem in the sensor reference voltage “B” circuit, potentially affecting various vehicle sensors. This condition can lead to erratic engine behavior, poor performance, and compromised drivability. Addressing it promptly helps maintain optimal engine function and vehicle reliability.

P0652 quick overview

Meaning	P0652: Sensor Reference Voltage “B” Circuit Low
Is it serious?	Yes, it can cause poor performance and drivability issues.
Possible causes	– Faulty sensors or wiring – ECM issues – Low voltage in the circuit
How to diagnose?	Check fuel filter and clean tank delivery units. Test fuel rail pressure sensor for proper voltage. Inspect wiring for corrosion or damage. Verify fuel delivery and pressure. Replace faulty parts like the fuel rail pressure sensor or N92 solenoid as needed.

How to fix P0652 – learn from mechanics

I looked into P0652 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Mercedes

Vehicle information 2005 Mercedes-Benz E320 CDI 3.2L

Issue + repair history

• Check engine light on
• Symptoms: Poor idle quality, hesitation, surge
• Trouble codes: P0192, P0652
• P0192 returns immediately after clearing, P0652 returns after a minute of running
• Idle fluctuates, acceleration is poor
• Replaced fuel filter, but P0192 persisted
• Tested fuel rail pressure sensor, found 5V reference missing with sensor plugged in, set P0193 (voltage too high) with sensor unplugged
• Replaced fuel rail pressure sensor

Other OBD2 Codes + Test Results

• OBD2 Codes: P0192 – Fuel rail pressure sensor voltage too low, P0652 – Sensor B circuit supply voltage too low
• Fuel rail pressure idle: 5800 psi datastream
• Fuel rail pressure WOT/load: 16675 psi data

Mechanic suggestions

• Replace fuel filter before replacing the fuel rail pressure sensor
• Clean tank and delivery units to ensure correct fuel delivery before replacing any parts
• Check fuel delivery to high-pressure pump before replacing other parts
• Verify return fuel quantity and flow rate to ensure correct pressure and volume of fuel delivery
• Consider checking the delivery units in the tank, as they can be defective in several cars

Final fix The issue was resolved by replacing the fuel rail pressure sensor, which restored proper operation of the fuel system and eliminated the trouble codes.

Case #2: Volkswagen

Vehicle information 2003 Volkswagen Golf GTI 1.8T 1.8L

Issue + repair history

• Intermittent trouble code P0652 (implausible signal)
• Transmission shifts fine initially, but after a couple of days, it fails to shift and records the P0652 code
• Idle stays in first gear when cold, shifts fine when warmed up
• Detected using Launch X431 Master scanner
• Referred to as a Mazda transmission, but actually has a Jatco 5-speed automatic transmission (09A)
• Shift control implausible signal
• Replaced N92 solenoid in the valve body to fix the issue

Other OBD2 Codes + Test Results

• No other OBD2 codes mentioned
• No specific test results provided

Mechanic suggestions

• Verify transmission fluid level at the right temperature using a EURO package scanner
• Check/Clean/Replace Vehicle Speed Sensor (G68)
• Check/Clean/Replace Gearbox Speed Sensor (G38)
• Check/Replace Multi-Function Switch (F125)
• Check/Replace Clutch and/or Valve Body
• Consider replacing the valve body if the transmission fails to shift when cold
• Inspect the module under the passenger floor for water damage
• Check the internal wiring harness in the transmission for any issues

Final fix Replacing the N92 solenoid in the valve body resolved the issue with the transmission, allowing it to shift properly even when cold.

Case #3: Jeep

Vehicle information 2009 Jeep Compass Sport 2.4L

Issue + repair history

• Intermittent trouble codes: P0652, P0653, P2127, P2138
• Vehicle goes into limp mode intermittently
• Replaced Accelerator Pedal Position (APP) sensor
• Inspected and lubricated harness connector with dielectric grease, terminals looked fine
• Found terminal corrosion at C104 inline harness connector

Other OBD2 Codes + Test Results

• No specific test results provided

Mechanic suggestions

• Check ground points for corrosion and spread terminals
• Inspect wiring in the driver’s side footwell, particularly pink wires near accelerator pedal connectors
• Check brake switch wiring
• Inspect wiring beside clutch, as wires may be shorting out on the floor near the pillar where they go into the door sill
• Examine Transmission Integrated Power Module (TIPM) wiring and harness back to the passenger compartment for worn-out insulation or corrosion
• Check main relay box for rust if located between the driver-side wheel well and front bumper
• Ensure wiring to all sensors (crank, cam, crankshaft position vehicle speed sensor) is intact and not corroded
• Verify if the model is equipped with three APP sensors
• Check splices in the harness under the driver’s door opening sill plate and behind the driver’s kick panel for corrosion

Final fix Cleaning corrosion at the C104 inline harness connector resolved the intermittent trouble codes and limp mode issue.

How to diagnose P0652

Diagnostic Step	Explanation
Replace fuel filter and pressure sensor	Preliminary steps for addressing fuel system issues.
Clean tank and delivery units	Ensures unobstructed fuel delivery.
Check wiring and connectors	Identifies electrical faults affecting sensor voltage.
Inspect valve body and solenoids in transmissions	For transmission-related symptoms, like in the Volkswagen case.
Clean corrosion from connectors	Resolves issues caused by poor electrical connections.

This overview, based on cases from Mercedes-Benz, Volkswagen, and Jeep, shows the diversity of P0652 implications and solutions, from simple sensor replacements to more complex electrical repairs.