Fixing error code P0560

**dowtrader** · 07-17-2008

Hi All,
Need some expert advise from you guys. I have 1998 Pontiac Grand Prix 3.8L supercharged with 170K kilometers. This car has become a worse nightmare for me. Since March this year it's giving me some electrical trouble which no body is able to understand. Error code P0560 (System voltage malfunction). This is an intermittent problem and my car just stalls and transmission doesn't want to shift the gears. I have to drive in 1 gear only. I changed a couple of alternators in 4 months. Both turned out faulty by overcharging. Changed battery and put the new interstate one. Problem still persists. Can somebody help me in resolving this error. Please help me. Your kind advise will be greatly appreciated. I can't tell you how much trouble i have been going thru both financially and mentally just because of this problem.

**quikgtp** · 07-17-2008

Some info on the code...

Circuit Description
The PCM monitors system voltage on the PCM ignition feed circuit. If the system voltage is out of tolerance, DTC P0560 will be set. When the conditions that set DTC P0560 are present, operation of some vehicle systems and components may be affected.

Conditions for Running the DTC
The engine is running.

Conditions for Setting the DTC
• System voltage monitored at the PCM ignition feed circuit is less than 9 volts or greater than 16 volts.

• Above conditions for longer than 25 seconds.

Action Taken When the DTC Sets
• The PCM will not illuminate the Malfunction Indicator Lamp (MIL).

• The PCM will store conditions which were present when the DTC set as Fail Records data only. This information will not be stored as Freeze Frame data.

• The PCM will default the transmission default to 3rd gear.

• The PCM will inhibit TCC operation.

Conditions for Clearing the MIL/DTC
• A history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.

• DTC can be cleared by using the scan tool Clear Info function or by disconnecting the PCM battery feed.

Diagnostic Aids
Check for the following conditions:

Important: Be sure to inspect PCM engine grounds for being secure and clean.

• Poor connection at PCM.

Inspect harness connectors backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal to wire connections.

• Damaged harness.

Inspect the wiring harness for damage. If the harness appears to be OK, observe the Ignition 1 voltage display on the scan tool while moving connectors and wiring related to the PCM, dash harness, and engine harness. A change in the display will indicate the location of the malfunction.

Important: Charging with a battery charger while starting the engine can cause DTC P0560 to be set.

If DTC P0560 cannot be duplicated, reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition. For complete information and additional diagnostics for the vehicle charging system, refer to Charging System Check .

This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.