Po651 sensor reference voltage b circuit/open

DTC P2138: Accelerator Pedal Position (APP) Sensor 1-2 Correlation

P2138
• The ECM detects that the voltage difference between APP sensor 1 and 2 is greater than 0.23 volt, 0.25 volt for LLT, with the pedal released.
• The ECM detects that the voltage difference between APP sensor 1 and 2 is greater than 0.29 volt, 0.31 volt for LLT, with a partially pressed pedal.
• The ECM detects that the voltage difference between APP sensor 1 and 2 is greater than 1.66 volts, 1.70 volts for LLT, with a fully pressed pedal.
• Any of the above conditions exist, then a 5 second delay for MIL ON.

Diagnostic Aids
Test the current output of the 5-volt reference circuits if you suspect high resistance in the circuit. The current output should be greater than 80 mA for APP 1 and greater than 50 mA for APP 2.


If you don't know how to test the 5 volt reference circuits you need to take it to a qualified repair shop.


Circuit/System Verification
Ignition ON, observe the DTC information with a scan tool. DTC P0651, P0652, P0653, P0697, P0698, or P0699 should not be set.
? If a DTC is set, refer to DTC P0641-P0643, P0651-P0653, or P0697-P0699.
Observe the scan tool APP Sensor voltage parameters. Verify both of the APP sensor voltages are between 0.74-4.82 V.
Rapidly depress the accelerator pedal from the rest position to the wide open throttle position (WOT) and release pedal. Repeat the procedure several times. DTCs P2122, P2123, P2127, P2128, or P2138 should not set.
Slowly depress the accelerator pedal to WOT and then slowly return the pedal to closed throttle. Repeat the procedure several times. DTCs P2122, P2123, P2127, P2128, or P2138 should not set.
Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
Ignition OFF, remove the fuse that supplies B+ to terminal 56-X2 of the ECM.
Disconnect the harness connector at the accelerator pedal assembly.
Test for less than 5 ? between the appropriate low reference circuit of the APP sensor and ground.
? If greater than the specified range, test the low reference circuit of the APP sensor for a short to voltage, or an open/high resistance. If the circuit/connections test normal, replace the ECM.
Install the fuse that supplies B+ to terminal 56-X2 of the ECM.
Note: The 5-volt reference circuit voltage can be within the specified range with a high resistance in the circuit. If this condition is suspected, refer to Diagnostic Aids.
Ignition ON, test for 4.8-5.2 V between the appropriate 5-volt reference circuit of the APP sensor and ground.
? If less than the specified range, test the 5-volt reference circuit for a short to ground or open/high resistance. If the circuit/connections test normal, replace the ECM.
? If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit/connections test normal, replace the ECM.
Observe the appropriate scan tool APP sensor voltage parameter. Verify the voltage is less than 0.3 volt.
? If greater than the specified range, test the signal circuit of the applicable APP sensor for a short to voltage. If the circuit/connections test normal, replace the ECM.
Connect a 3 A fused jumper wire between the appropriate signal circuit and the 5-volt reference circuit of the APP sensor. Verify the APP sensor voltage parameter is greater than 4.8 V.
? If less than the specified range, test the appropriate signal circuit for a short to ground or an open/high resistance. If the circuit/connections test normal, replace the ECM.
? If both APP sensor voltage parameters display greater than 4.8 V test the signal circuits of the APP sensors for a shorted together condition. If the circuit/connections test normal, replace the ECM.
If all circuits/connections test normal, test or replace the accelerator pedal assembly.

DTC P0532: Air Conditioning A/C Refrigerant Pressure Sensor Circuit Low Voltage
The sensor gets 5 volt ref. voltage from the ECM - engine control module . Three wire sensor , all wires are to an from the ECM .

Circuit/System Description
The engine control module (ECM) monitors the high side refrigerant pressure through the A/C refrigerant pressure sensor. The ECM supplies a 5-volt reference and a low reference to the sensor. Changes in the A/C refrigerant pressure cause the A/C refrigerant pressure sensor signal to the ECM to vary. When the pressure is low, the signal voltage is low. When the pressure is high, the ECM commands the cooling fans on. When pressure is too high or too low, the ECM will not allow the A/C compressor clutch to engage.

Circuit/System Testing
Ignition OFF, disconnect the harness connector at the A/C refrigerant pressure sensor.
Ignition OFF, test for less than 10 ohms between the low reference circuit terminal 1 and ground.
? If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 2 and ground.
? If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
? If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.
Verify the scan tool A/C High Side Pressure Sensor parameter is less than 0.1 volts (1 psi).
? If greater than the specified range, test the signal circuit terminal 3 for a short to voltage. If the circuit tests normal, replace the ECM.
Install a 3A fused jumper wire between the signal circuit terminal 3 and the 5-volt reference circuit terminal 2. Verify the scan tool A/C Refrigerant High Side Pressure Sensor parameter is greater than 4.90 volts (425 psi).
? If less than the specified range, test the signal circuit for short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
If all circuits test normal, test or replace the A/C refrigerant pressure sensor.

A/C Refrigerant Pressure Sensor
In the engine compartment, on the high pressure refrigerant line

Do you know difference between high an low side lines ?
between alternator an the compressor

DTC P0651: 5-Volt Reference 2 Circuit First off do you know what computer reference voltage is ? Your vehicle has 2 reference voltage circuits . This reference voltage is used to power engine sensors .
Diagnostic Fault Information
Circuit
Short to Ground
Open/High Resistance
Short to Voltage
Signal Performance
Accelerator Pedal Position (APP) Sensor 1 5-Volt Reference 2 Circuit
P0651
P2122
P0651
--
Accelerator Pedal Position (APP) Sensor 2 5-Volt Reference 1 Circuit
P0641
P2127
P0641
--
Air Conditioning (A/C) Refrigerant Pressure Sensor 5-Volt Reference 1 Circuit
P0641
P0532
P0641
--
Crankshaft Position Sensor 5-Volt Reference 2 Circuit
P0651
P0335
P0651
--
Fuel Tank Pressure (FTP) Sensor 5-Volt Reference 1 Circuit
P0641
P0452
P0641
--
Intake Camshaft Position Sensor 5-Volt Reference 1 Circuit
P0641
P0340
P0641
--
Manifold Absolute Pressure (MAP) Sensor 5-Volt Reference 1 Circuit
P0641
P0107
P0641
--
Secondary Air Injection (AIR) Solenoid 5-Volt Reference 2 Circuit
P0651, P2432
P2431
P0651, P2431
--
Throttle Position (TP) Sensor 1 5-Volt Reference 2 Circuit
P0651
P0122
P0651
--
Throttle Position (TP) Sensor 2 5-Volt Reference 2 Circuit
P0651
P0222
P0651
--

How to check the 5v reference circuit for short to ground Cadillac

You may need the shop manual for this.
First, it depends on the make model and year.
Code 651 generally means the computer is not "seeing" a 5 volt reference on a particular circuit. It does not always mean a sensor is faulty.
You would need to figure out which circuit is involved, and check it with a meter.

code p2045 refers to reductant temperature sensor--high input==causes --wiring faulty sensor
code p2197 refers to heated oxygen sensor(HO2S)1 bank 2-- signal stuck lean===causes HO2S---fuel pressure---injectors---intake leak
also refers to oxygen sensor (O2s)1 bank 2 -signal stuck lean===causes--O2S--fuel pressure---injectors---intake leak
also refers to heated oxygen sensor (HO2S) 1 bank 2--implausible signal===causes wiring---short to ground--short to positive--HO2S---ECM
code po190 refers to fuel rail pressure (FRP) sensor-circuit malfunction===causes --wiring ---fuel rail pressure sensor---ECM
code p2247 refers to heated oxygen sensor (HO2s) 1 bank 1 reference voltage--open circuit===causes--wiring ---ho2s
also refers to o2s 1 bank 2 reference voltage ---open circuit===causes wiring---o2s
also refers to HO2S 1 bank 2 ---no signal===causes wiring--ho2s---ECM
code p2245 refers to HO2S 1 bank 1 --reference voltage --circuit low===causes--wiring short to ground--ho2s also refers to o2s 1 bank 1 circuit low===causes wiring short to ground--o2s
code p2248 refers to the ho2s I bank --performance problem===causes --wiring--ho2s
code p2249 has the same causes short to ground---ho2s and o2s
code p2518 refers to a/c refrigerant pressure sensor B ---circuit high===causes wiring short to positive--a/c refrigerant pressure sensor.
so after all that replace all the ho2s and o2s sensors using the correct tools so that the wiring is not damaged and check the wiring back to the ECM for burns and rub marks.

Hi there:

DTC P0641 - 5-Volt Reference 1 Circuit

DTC P0651 - 5-Volt Reference 2 Circuit

Diagnostic Fault Information
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

Circuit/System Description
The engine control module (ECM) has 2 internal 5-volt reference busses called 5-volt reference 1 and 5-volt reference 2. Each reference bus provides 5-volt reference circuits for more than one sensor. Therefore, a fault condition on one 5-volt reference circuit will affect the other 5-volt reference circuits connected to that reference bus. The ECM monitors the voltage on the 5-volt reference busses.

The 5-volt reference 1 bus provides 5 volts to the following sensors:
* The manifold absolute pressure (MAP) sensor
* The fuel tank pressure (FTP) sensor
* The air conditioning (A/C) refrigerant pressure sensor
* The accelerator pedal position (APP) sensor 2
* The intake camshaft position (CMP) sensor

The 5-volt reference 2 bus provides 5 volts to the following sensors:
* The APP sensor 1
* The throttle position (TP) sensor 1 and 2
* The crankshaft position (CKP) sensor

Conditions for Running the DTC
* DTCs P0601, P0602, P0603, P0604, P0605, P0606, P0607, and P2610 are not set.
* The ignition is in Unlock, Accessory, Run, or Crank.
* The ignition voltage is more than 5.23 volts.
* DTCs P0641 and P0651 run continuously when the above conditions are met.

Conditions for Setting the DTC
The ECM detects a voltage out of tolerance condition on the 5-volt reference 1 or 2 bus for more than 0.5 second.

Action Taken When the DTC Sets
DTCs P0641 and P0651 are Type A DTCs.

Conditions for Clearing the MIL/DTC
DTCs P0641 and P0651 are Type A DTCs.

Diagnostic Aids
It may be possible to locate the fault by disconnecting one component at a time from the 5-volt reference circuit while viewing the 5-Volt Reference circuit parameter on the scan tool. The scan tool parameter would change from Fault to OK when the source of the fault is disconnected.

If all 5-volt reference components have been disconnected and a Fault is still indicated, the fault may exist in the wiring harness.

Circuit/System Verification
With the ignition ON and the engine OFF, observe the 5-volt Reference 1 and 2 parameters. The scan tool should display 4.3-4.7 volts for a normally operating system.

Circuit/System Testing
Important: Additional DTCs will set when disconnecting the components.

1. Ignition OFF, disconnect the harness connector of all appropriate sensors for the applicable DTC.

Important: A short to voltage on the signal circuit of certain components may cause this DTC to set.

2. Ignition ON, measure for 4.8-5.2 volts between one of the 5-volt reference circuits and ground.

* If the voltage is less than the specified value, test for a short to ground on all the 5-volt reference circuits. If all circuits test normal, replace the control module.
* If the voltage is greater than the specified value, test for a short to voltage on all the 5-volt reference circuits, or the signal circuit, for each component associated with the appropriate 5-volt reference circuit. If all circuits test normal, replace the control module.

3. Connect each component associated with the 5-volt reference circuit, one at a time, while monitoring the voltage. The voltage should not change more than 1 volt.

* If the voltage display changes more than the specified value when a component is connected, replace the component.


Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day.

Yes here is that list.
Chrysler products COMMON CODES OBD1 (vehicles made before 1995)
Part 1: Chrysler Domestic vehicles
CODES/Meaning
88 display used for start or test
11 camshaft signal or ignition signal, no reference signal during cranking
12 memory to controller has been cleared within 50-100 engine starts
13 map sensor not detecting any change during test
14 map voltage too high or too low
15 vehicle speed sensor, no signal detected
16 knock sensor circuit. open or short detected
17 low engine temperature, possible thermostat fault
21 oxygen sensor signal, neither rich or lean detected
22 coolant sensor voltage low
23 air charge voltage high/low detected
24 throttle positioner sensor voltage high/low
25 automatic idle speed motor driver circuit, short or open detected
26 injectors 1,2,3 peak current not reached
27 injector control circuit does not respond to control signal
31 purge solenoid circuit, open or short detected
32 egr solenoid circuit, open or short detected
33 a/c clutch relay circuit, open or short detected
34 speed control servo solenoid, open or short detected
35 radiator fan control relay circuit, open or short detected
36 wastegate solenoid, open or short detected
37 part throttle unlock(PTU) circuit, open or short detected
41 charging system circuit not responding to control signal
42 fuel pump or auto shutdown (ASD) relay voltage sensed at controller
43 ignition control circuit not responding
44 battery temperature voltage circuit problem
45 turbo boost limit exceeded-map sensor detects overboost
46 battery voltage too high
47 battery voltage too low
51 air/fuel at limit
52 logic module fault
53 internal controller failure
54 camshaft reference circuit not detected
55 end of message
61 baro read solenoid, open or short detected
62 emr mileage not stored
63 eeprom write denied
64 flex fuel sensor signal out of range
65 manifold tuning valve, open or short detected
66 no ccd messages
76 ballast bypass relay, open or short detected
77 speed control relay, open or short detected

P0107 - Manifold Absolute Pressure/Barometric Pressure Circuit Low Input

The Manifold Absolute Pressure (MAP) sensor responds to changes in the intake manifold pressure (vacuum). 5 Volts is supplied to the sensor from the PCM (powertrain control module). Inside the MAP sensor is a resistor that moves in relation to manifold pressure. The resistor varies the voltage between about 1 volt to 4.5 volts (depending on engine load) and that voltage signal is returned to the PCM to indicate manifold pressure (vacuum). This signal is essential for the PCM to determine fuel delivery. A P0107 DTC is set when the PCM sees that the MAP signal voltage is less than .25 volts which is too low.

Potential Symptoms: Anytime the MAP sensor signal is low the vehicle will likely have a very difficult time starting. Other symptoms may include:
* Hard to start
* Long cranking times
* Sputtering/missing
* Blowing black smoke
* Poor fuel economy
* Dies intermittently
* MIL(Malfunction Indicator Lamp) illumination

Causes: The causes of a low MAP sensor signal circuit (P0107) could be any of the following:
* Bad MAP sensor
* Open or short in the signal circuit
* Open or short in the 5 Volt reference circuit
* Ground circuit open or shorted
* Bad PCM

Possible Solutions: First, using a scan tool with the Key on and engine running, monitor the MAP sensor voltage. If it is reading less than .5 volts, turn engine off, unplug the MAP sensor and, using a DVOM (Digital Volt/Ohm Meter) check for 5Volts on the 5 Volt reference circuit.

1. If there is not 5 Volts on the reference circuit, then check for the reference voltage at the PCM connector. If it is present at the PCM connector but not the MAP connector, repair the open in the reference circuit between the PCM and MAP harness connector. If 5 Volt reference is NOT present at the PCM connector, check powers and grounds of PCM and repair/replace as needed. (NOTE: On Chrysler products, a shorted Crank sensor, Vehicle speed sensor or any other sensor that utilizes the 5 Volt reference from the PCM can short out the 5 Volt reference. To fix simply unplug each sensor one at a time until the 5 Volt reference reappears. The last sensor unplugged is the shorted sensor.)

2. If you have a 5 Volt reference at the MAP connector, jumper the 5 volt reference circuit to the signal circuit. Now check the MAP voltage on the scan tool. It should be 4.5 to 5 Volts. If it is, replace MAP sensor. If not, repair open/short in the signal circuit wiring and re-check.

3. If all appears okay, perform a wiggle test. Start engine and manipulate the harness, connector and tap on the MAP sensor. Note any changes in voltage or engine speed. Repair connector, harness, or sensor as needed.

4. If the wiggle test checks out, use a vacuum pump (or just use your lungs) to draw a vacuum on the MAP sensor vacuum port. As you add vacuum the voltage should decrease. With no vacuum, the MAP sensor should read approximately 4.5 volts. If there is no change in MAP sensor reading on the scan tool, replace MAP sensor.

MAP Sensor DTC's: P0105, P0106, P0107, P0108 and P0109.

Hope helps (remember rated and comment this).

The Manifold Absolute Pressure (MAP) sensor responds to changes in the intake manifold pressure (vacuum). 5 Volts is supplied to the sensor from the PCM (powertrain control module). Inside the MAP sensor is a resistor that moves in relation to manifold pressure. The resistor varies the voltage between about 1 volt to 4.5 volts (depending on engine load) and that voltage signal is returned to the PCM to indicate manifold pressure (vacuum). This signal is essential for the PCM to determine fuel delivery. A P0107 DTC is set when the PCM sees that the MAP signal voltage is less than .25 volts which is too low.

Potential Symptoms Anytime the MAP sensor signal is low the vehicle will likely have a very difficult time starting. Other symptoms may include:

• Hard to start
• Long cranking times
• Sputtering/missing
• Blowing black smoke
• Poor fuel economy
• Dies intermittently
• MIL(Malfunction Indicator Lamp) illumination

Causes The causes of a low MAP sensor signal circuit (P0107) could be any of the following:

• Bad MAP sensor
• Open or short in the signal circuit
• Open or short in the 5 Volt reference circuit
• Ground circuit open or shorted
• Bad PCM

Possible Solutions First, using a scan tool with the Key on and engine running, monitor the MAP sensor voltage. If it is reading less than .5 volts, turn engine off, unplug the MAP sensor and, using a DVOM (Digital Volt/Ohm Meter) check for 5Volts on the 5 Volt reference circuit.
1. If there is not 5 Volts on the reference circuit, then check for the reference voltage at the PCM connector. If it is present at the PCM connector but not the MAP connector, repair the open in the reference circuit between the PCM and MAP harness connector. If 5 Volt reference is NOT present at the PCM connector, check powers and grounds of PCM and repair/replace as needed. (NOTE: On Chrysler products, a shorted Crank sensor, Vehicle speed sensor or any other sensor that utilizes the 5 Volt reference from the PCM can short out the 5 Volt reference. To fix simply unplug each sensor one at a time until the 5 Volt reference reappears. The last sensor unplugged is the shorted sensor.)
2. If you have a 5 Volt reference at the MAP connector, jumper the 5 volt reference circuit to the signal circuit. Now check the MAP voltage on the scan tool. It should be 4.5 to 5 Volts. If it is, replace MAP sensor. If not, repair open/short in the signal circuit wiring and re-check.
3. If all appears okay, perform a wiggle test. Start engine and manipulate the harness, connector and tap on the MAP sensor. Note any changes in voltage or engine speed. Repair connector, harness, or sensor as needed.
4. If the wiggle test checks out, use a vacuum pump
(or just use your lungs) to draw a vacuum on the MAP sensor vacuum port. As you add vacuum the voltage should decrease. With no vacuum, the MAP sensor should read approximately 4.5 volts. If there is no change in MAP sensor reading on the scan tool, replace MAP sensor.

CODE PO452 FUEL TANK PRESSURE SENSOR CIRCUIT LOW INPUT CONDITIONS.YOUR FTP OR FUEL TANK PRESSURE SENSOR FAILED. PO651 5 VOLT REFERENCE 2 CIRCUIT MALFUNCTION CONDITIONS.POSSIBLE CAUSE 5 VOLT REF.CIRCUIT IS SHORTED TO CHASSIS OR SENSOR GROUND.OR 5 VOLT REF CIRCUIT TO MAP OR TP SENSORS CIRCUIT IS SHORTED TO B+.ALSO YOUR PCM HAS FAILED.YOU PROBABLY NEED TO TAKE IT TO DEALERSHIP.THEY HAVE DIAGNOSTIC EQUIPMENT TO CHECK SENSORS AND PCM FAILURE.