Computer not seeing proper 8 volt referance - 2003 Chrysler Town & Country

DTC P1635

Circuit Description
The powertrain control module (PCM) uses the 5-volt reference 1 circuit as a sensor feed to the following sensors:
• The throttle position (TP) sensor
• The manifold absolute pressure (MAP) sensor
• The exhaust gas recirculation (EGR) valve pintle position sensor
The PCM monitors the voltage on the 5-volt reference 1 circuit. If the voltage is out of tolerance, the PCM will set DTC P1635.


3
Inspect the PCM and the engine grounds. Ensure that the grounds are clean and secure.
If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.
Was a problem found?
--
YES Go to Step 13
NO Go to Step 4
4
Turn OFF the ignition.
Disconnect the EGR valve electrical connector.
Turn ON the ignition, with the engine OFF.
Using a DMM, measure voltage between the 5-volt reference circuit and engine ground.
Is the voltage near the specified value?
5 V
YES Go to Step 6
NO Go to Step 5
5
Is the voltage more than the specified value?
5 V

Reconnect the EGR valve.
Disconnect TP sensor.
Using a DMM, measure voltage between the 5-volt reference 1 circuit and the engine ground.
Is the voltage near the specified value?
5 V
YES Go to Intermittent Conditions
NO Go to Step 10
7
Monitor the DMM while disconnecting all other devices connected to the 5-volt reference circuit one at a time.
If voltage changes when one of the above components are disconnected, replace the component. Refer to the appropriate replacement procedure.
Was a component replaced?
--
YES Go to Step 13
NO Go to Step 8
8
Turn OFF the ignition.
Disconnect the PCM.
Inspect the 5-volt reference circuit for a short to ground or for any sensor low reference circuit.
If a condition is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.
Was a problem found?
--
YES Go to Step 13
NO Go to Step 12
9
Turn OFF the ignition.
Disconnect the PCM.
Turn ON the ignition, with the engine OFF.
Inspect the following circuits for a short to voltage:
• The 5-volt reference circuit
• The MAP sensor signal circuit
If a condition is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.
Was a condition found?
--
Go to Step 13
Go to Step 12
10
Inspect for a short between the EGR control high circuit and the 5-volt reference circuit, and repair as necessary. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct a condition?
--
Go to Step 13
Go to Step 11
11
Replace the EGR valve. Refer to Exhaust Gas Recirculation Valve Replacement .
Did you complete the replacement?
--
Go to Step 13
--
12
Replace the PCM. Refer to Powertrain Control Module Replacement .
Did you complete the replacement?
--
Go to Step 13
--
13
Use the scan tool in order to clear the DTCs.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC run and pass?

Light's on the switch are controlled by the transfer case shift control module . Your best bet , take your vehicle to a qualified repair shop that has diagnostic scanner that can read code's in the module . Not OBD 2 code reader , won't work . Need factory GM tech 2 scan tool or some other professional scan tool .
DTC B2725
Circuit Description
The accessory switch circuit consists of 4 modes. The transfer case shift control module supplies 5 volts to the switch through the switch signal circuit. The current travels through the resistor of the currently active mode. The current on the switch signal circuit is monitored by the transfer case shift control module. The voltage on the switch signal circuit will vary depending on which mode button is pressed by the driver.
The transfer case shift control module constantly monitors the switch signal circuit to determine the condition of the accessory switch circuit.
When each of the modes are selected they complete a circuit through their own specific resistor. The transfer case shift control module continuously monitors the switch signal circuit to determine whether the Neutral, 2HI, 4HI, or 4LO mode was selected by the driver.

DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B2725 ATC Mode Switch Circuit Malfunction

This step test the switch signal low circuit for an open, or high resistance.
Step
Action
Values
Yes
No
Schematic Reference: Transfer Case Control Schematics
Connector End View Reference: Transfer Case Control Connector End Views
1
Did you perform the Diagnostic System Check - Vehicle?
--
Go to Step 2
Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2
With the accessory switch disconnected, connect a DMM between the low reference signal circuit and the 5-volt reference circuit at the switch.
Measure the resistance through the accessory switch while pressing and holding each of the mode buttons and comparing values.
Does the DMM indicate all resistance values within the specified ranges?
4 HI: 656.2-669.4 ohms
2 HI: 1.50-1.53 K ohms
Neutral: 1.010-1.031 K ohms
4 LO: 2.32-2.36 K ohms
Normal: 9.00-9.18 K ohms
Go to Step 3
Go to Step 6
3
Disconnect the accessory switch from the wiring harness.
Turn ON the ignition.
With a DMM, probe the 5-volt reference circuit.
Was the voltage reading within the specified values?
4.8-5.2 V
Go to Step 5
Go to Step 4
4
Test the 5-volt reference circuit for a short to voltage, a short to ground, an open, or a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 8
Go to Step 7
5
Test the switch signal low circuit for an open or high resistance. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 8
Go to Step 7
6
Replace the accessory switch. Refer to Accessory Switch Replacement in Instrument Panel, Gages and Console.
Did you complete the repair?
--
Go to Step 8
--
7
Replace the transfer case shift control module. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.
Did you complete the repair?
--
Go to Step 8
--
8
Use the scan tool in order to clear the DTCs.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC set?
--
Go to Step 2
System OK

What engine ?
Engine Controls and Fuel - 3.5L
Engine Controls and Fuel - 3.9L
Engine Controls and Fuel - 5.3L

DTC P0069: Manifold Absolute Pressure-Barometric Pressure Correlation

Circuit/System Description
The BARO sensor has a 5-volt reference circuit, a low reference circuit, and a signal circuit. The control module supplies 5 volts to the BARO sensor on a 5-volt reference circuit, and provides a ground on a low reference circuit. The BARO sensor provides a voltage signal to the control module on a signal circuit relative to the ambient pressure changes.
The manifold absolute pressure (MAP) sensor has a 5-volt reference circuit, a low reference circuit, and a signal circuit. The control module supplies 5 volts to the MAP sensor on a 5-volt reference circuit, and provides a ground on a low reference circuit. The MAP sensor provides a voltage signal to the control module on a signal circuit relative to the intake manifold pressure changes. The control module compares the BARO sensor to the MAP sensor in order to monitor the BARO sensor operation.


DTC C0899 : Device Voltage Low

Circuit/System Description
The electronic brake control module (EBCM) monitors the ignition voltage level available for system operation. A low voltage condition prevents the system from operating properly.

Circuit/System Testing
Measure the voltage at the battery terminals.
? If less than 12 volts, charge and test the battery.
With a scan tool, read the ignition voltage in the EBCM data list. Verify that battery terminal voltage and ignition voltage readings do not differ more than 1 volt.
? If the difference is more than 1 volt, test the ground circuit of the EBCM for high resistance or replace the EBCM.
If OK, test the charging system.

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

The ECT sensor needs a power and ground to operate. It uses resistance to create a signal that is sent back to the computer. You can use a volt meter and check the plug for a 5 volt reference on one wire and the other wire will be a ground. If no 5 volt reference, look for a burned out fuse or broken/damaged wiring. A scan tool that shows data would be very helpful in knowing what the sensor is reading. The sensor may be reading properly and the problem may be due to a low coolant level or defective thermostat

DTC P1635
The powertrain control module (PCM) provides 5 volts to the following sensors:
?€¢
The manifold absolute pressure (MAP) sensor

?€¢
The exhaust gas recirculation (EGR) valve

?€¢
The fuel tank pressure (FTP) sensor

?€¢
The throttle position (TP) sensor

These 5-volt reference circuits are independent of each other outside the PCM, but are bussed together inside the PCM. Therefore a circuit condition on one sensor 5-volt reference circuit may affect the other sensor 5-volt reference circuits. The PCM monitors the voltage on the 5-volt reference circuit. If the PCM detects that the voltage is out of tolerance, DTC P1635 sets.
Diagnostic Aids
?€¢
If any sensor using a 5-volt bias voltage, such as the intake air temperature (IAT) sensor or fuel sensor, is shorted to voltage, DTC P1639 may set in addition to DTC P1635.

?€¢
For an intermittent condition, refer to Intermittent Conditions .

Does the vehicle start an run ?

Both crank and cam sensors have a 8 volt reference I have found the wiring melted together where it cross over transmission shorting out the signal. also test your reference voltage at the computer with circuit unplugged at sensor watch meter and wiggle wiring going back to computer this will help find faulty area.

The easiest way to find out about the voltage is to check the other sensors which would be on the same circuit. The engine temp sensor, Oxygen sensor, or MASS air flow sensor would be possible choices. This was one of the first years for fuel injection so the computer is a very simple setup compared to today.
On models built after 1990 the reference voltage is 5 volts. But on early models it could have been more.
Either way, the sensors get their power from the computer.
Normally you would install the TPS and set it at .5 volts with the throttle closed.

you will need to some testing to islate problem

Turn ON the ignition, with the engine OFF.
Disconnect the MAP sensor.
Connect a voltmeter between the MAP sensor 5-volt reference circuit and a good ground.
Measure for a proper range of 4.8-5.2 volts between the MAP sensor 5-volt reference circuit and a good ground.
If the voltage is less than the specified range, then test the circuit for a high resistance. If the is normal, replace the ECM. If the voltage is more than the specified range, then test the circuit for a short to voltage. If the circuit is normal, replace the ECM.With the MAP sensor still disconnected, use the scan tool to observe the MAP Sensor parameter for the proper value of less than 12 kPa.
If the MAP Sensor parameter is more than 12 kPa, then test the MAP sensor signal circuit for a short to voltage. If the circuit is normal, replace the ECM.Connect a jumper wire between the MAP sensor 5-volt reference circuit and the MAP sensor signal circuit.
Use the scan tool to observe the MAP Sensor parameter for the proper value of more than 103 kPa.
If the MAP Sensor parameter is less than 103 kPa, then test the MAP sensor signal circuit for a high resistance. If the circuit is normal, replace the ECM.Turn OFF the ignition, and all electrical accessories. Allow sufficient time for the control module to power down before taking a resistance measurement.
Measure for a proper value of less than 5 ohms of resistance between the low reference circuit of the MAP sensor and a good ground.
If the resistance is more than 5 ohms, then test the circuit for a high resistance. If the circuit tests normal, replace the ECM.If the MAP sensor circuits test normal, then replace the MAP sensor.

make sure injector gets 12 volts from ASD relay. then hook a volt meter from positive side of battery to injector driver circuit, it should fluctuate while trying to start. check fuel injector, should ohm at 12-13 ohms if lower it could be shorted......if the pcm injector driver is bad, the only fix is a new computer. you really need s scanner to properly diagnose this.