How much volt - Cars & Trucks

Do you know anything about ECM five volt reference circuit's ?
DTC P0641: 5-Volt Reference 1 Circuit
The engine control module (ECM) has 3 internal 5-volt reference busses called 5-volt reference 1, 5-volt reference 2, and 5-volt reference 3. 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 clutch apply sensor
• The fuel rail sensor
• The fuel tank pressure (FTP) sensor
• The intake air pressure and temperature sensor

You have a shorted sensor more then likely or wiring problem . Suggest you watch this video .
How to check the 5v reference circuit for short to ground Cadillac

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

What are the OBD2 fault codes in memory?

if the charge light is going out after starting then it is charging. Next step is to use a multimeter that has the ability to read volts DC and volts AC. If it shows Volts dc 13.5 to 14.5 volts at around 2.000rpms then it is good . If it shows volts ac then the rectifier in the alternator is not working and needs replacing . Next place an amp meter in the line to the battery and read the amperage .It will read in a ratio to the volts DC so if the volts Dc is up around 14.5 then the current flow will be low but if it reads 12 volts then the current will be high. If the volts dc is over 14.5 volts say 16 volts then the current will be high as the regulator is not controlling the current out put. If this sound daunting then go to an accredited auto electrical shop and have it checked out

P0641 Chevrolet Description
The control module has 2 internal 5-volt reference buses called 5-volt reference 1 and 5-volt reference 2 . Each reference bus provided 5-volt reference circuit 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 the reference bus. The control module monitors the voltage on the 5-volt reference buses.


Read more: http://engine-codes.com/p0641_chevrolet.html#ixzz3Kg3EaTQP

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.


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Do you have any indication that the battery is not being charged properly, such as slow cranking speed when trying to start?
With the engine not running, the battery (fully charged) should show about 12.5 volts with a voltmeter. With the engine running at normal (not idle) speed, the voltage should be 13.5 - 14.5 volts depending on the state of charge of the battery. At idle, the voltage may drop below 13.5 volts depending on how many accessories you have turned on (headlights, a/c, blower motor, radio, etc). If the 12.8 - 12.9 volts you referenced is at idle with accessories on, but increases when you increase engine speed, you're probably OK.

No resistance to check or adjust, with key on, one wire will have 5.0 volts, the next one should have about .50 (1/2) volt give or take .10 volts, the last wire is ground, check with volt meter, connect ground from volt meter on to battery ground, and probe with pos. probe, the wire with 5 volts is out put from ECM, and the one with .50 volts is in put to ECM, to check TPS, on the wire with .50 volts, as you open throttle voltage should go up to 5.0 volts, with no drop in voltage, as you open throttle, if there is voltage drop, bad TPS, to adjust, on wire with .50 volts, with key on, engine off, should read .50 volts, if more or less volts, loosen screws on TPS and adjust to .50 volts, hope this was very helpful.

A 12 volt battery is actually 13.2 volts fully charged. If you are reading 16 volts, you are probably getting extranious voltage from the system somewhere, especially if the vehicle is running when you check the voltage. The alternator will put out about 15-18 volts to charge the battery normally, and yours may put out 28-32 volts to charge them in series, but the batteries, when disconnected, should never read more than about 13.2 volts each. Typically, it will read about 12 1/2 volts when disconnected. COMPLETELY DISCONNECT BOTH OF THE BATTERIES. If you still read 16 volts when it is disconnected, you must have a bad meter because the battery can't produce that much voltage, no matter what. (Six 2.2 volt cells connected in series inside the case.) Put the meter on a known good battery on another car that is not running and see if you get the same reading. It sounds like the other battery is almost dead, regardless, and it sounds like your series/parallel switch may be malfunctioning. (That is the switch that puts the battery in series to run the 24 volt starter, then puts the batteries in parallel to run the remainder of the vehicle on 12 volts. This is all assuming that you have a diesel vehicle with a 24 volt starter and that is why you have two batteries.