Engine Controls - System & Component Testing: Other Mitsubishi Diamante II

Turbocharger Pressure Check

1. Disconnect Black turbocharger pressure control hose at wastegate solenoid valve, and plug valve nipple. Attach pressure gauge to hose. Drive vehicle and accelerate engine, in 2nd gear, to 3500 RPM or more. Check turbocharger pressure when pressure gauge stabilizes. See «TURBOCHARGER PRESSURE SPECIFICATIONS»(ref-91126-S22983409072001030200000) table. TURBOCHARGER PRESSURE SPECIFICATIONS Application psi (kPa) Eclipse 6.4-14.7 (44-101) 3000GT 2.9-8.7 (20-60)
2. If pressure gauge reading is more than specified, check operation of wastegate actuator and valve, and for a disconnected or cracked waste gate actuator hose. See DTCs P1103 and P1104 in appropriate SELF-DIAGNOSTICS article. If pressure gauge reading is less than specified, check operation of wastegate actuator, and check for turbocharger pressure leaks or faulty turbocharger. Replace components as necessary.

Air By-Pass Valve

Remove air by-pass valve. Valve is mounted to intake air duct between air-to-air intercooler and intake plenum. Apply vacuum to diaphragm of vacuum valve. Valve should begin opening at approximately 16 in. Hg. Observe operation of valve through by-pass opening. Replace air by-pass valve if operation is not as specified.

Fuel Pressure Solenoid (Eclipse 2.0L Turbo)

1. Disconnect fuel pressure solenoid electrical connector. Check resistance across fuel pressure solenoid terminals. Resistance should be 36-44 ohms at 68°F (20°C).
2. Mark and disconnect vacuum hoses from fuel pressure solenoid. Connect hand vacuum pump to fuel pressure solenoid nipple at terminal end of solenoid. Connect jumper wires between fuel pressure solenoid terminals and battery positive terminal and battery negative terminal.
3. Apply vacuum with battery voltage applied. Vacuum should hold. Disconnect battery voltage and apply vacuum. Vacuum should leak. Cover nipple at opposite end of fuel pressure solenoid and apply vacuum. Vacuum should hold.

CONTROL UNIT

Note. For Engine Control Module (ECM) or Powertrain Control Module (PCM) location, see POWERTRAIN CONTROL MODULE (ECM/PCM) LOCATION table. To identify ECM/PCM power and ground terminals, see appropriate pin voltage chart in PIN VOLTAGE CHARTS article. To identify ECM/PCM power and ground circuits, see appropriate wiring diagram in WIRING DIAGRAMS article. (Scheme 91)- (Scheme 99).

POWERTRAIN CONTROL MODULE (ECM/PCM) LOCATION

Ground Circuits

1. Turn ignition off. Backprobe and check for continuity between chassis ground and ECM/PCM ground terminal(s). If continuity exists, go to next step. If continuity does not exist, repair open circuit between ECM/PCM connector and chassis ground. Ensure suspect ground connection is clean and tight.
2. Backprobe and measure voltage between chassis ground and ECM/PCM ground terminal(s). With engine operating at normal operating temperature, voltage should be less than one volt. If voltage is more than one volt, check for open, corrosion or loose connection in ground circuit.

Power Circuits

Turn ignition on. Backprobe and check for battery voltage at ECM/PCM power terminals. If battery voltage is not present, check operation of MFI relay. See RELAYS under MOTORS, RELAYS & SOLENOIDS. If relay is okay, check suspect circuit between ECM/PCM and relay. Perform repairs as necessary.

Scheme 91

Scheme 92

Scheme 93

Scheme 94

Scheme 95

Scheme 96

Scheme 97

Scheme 98

Scheme 99

ENGINE SENSORS & SWITCHES

Note. For circuit identification, see appropriate wiring diagram in WIRING DIAGRAMS article.

Barometric Pressure Sensor

Sensor is a part of volume airflow sensor assembly. See appropriate SELF-DIAGNOSTICS article.

Engine Coolant Temperature (ECT) Sensor

Disconnect ECT sensor connector. Check resistance between ECT sensor terminals. See appropriate ECT SENSOR RESISTANCES table.

ECT SENSOR RESISTANCES - ECLIPSE 2.0L NON-TURBO

ECT SENSOR RESISTANCES - ALL EXCEPT ECLIPSE 2.0L NON-TURBO

Heated Oxygen Sensor (HO2S)

Note. For circuit identification and wire colors, see appropriate wiring diagram in WIRING DIAGRAMS article.

1. Disconnect suspect HO2S 4-pin connector and connect test harness set to sensor. Using a test harness set, measure HO2S heater resistance between sensor terminals. See appropriate wiring diagram in WIRING DIAGRAMS article. If resistance is as specified, go to next step. See «HO2S HEATER RESISTANCE»(ref-91126-S15532257382001030200000) table. If resistance is not as specified, replace HO2S and recheck system proper operation. HO2S HEATER RESISTANCE HO2S Location (1) (2) Ohms Diamante Front (Calif.) 4.5-8.0 Front (Fed.) 7.0-40.0 Rear (All) 7.0-40.0 Eclipse 2.0L Non-Turbo Front & Rear (All) (3) 2.0L Turbo Front & Rear (All) 11.0-18.0 2.4L Front & Rear (Calif.) 2.5-5.0 Front & Rear (Fed.) 11.0-18.0 Galant Front & Rear (All) 11.0-18.0 Mirage 1.5L Front & Rear (All) 4.5-8.0 1.8L Front (Calif.) 4.5-8.0 Front (Fed.) 11.0-18.0 Rear (All) 11.0-18.0 Montero Front & Rear (All) 11.0-18.0 Montero Sport 2.4L Front & Rear (All) 7.0-40.0 3.0L & 3.5L Front (Calif.) 4.5-8.0 Front (Fed.) 7.0-40.0 Rear (All) 7.0-40.0 3000GT Front & Rear (All) 11.0-18.0 (1) Measured at 68°F (20°C). (2) HO2S output voltage measured while racing engine should be 0.6-1.0 volt when engine coolant temperature is 176°F (80°C) or more. (3) No resistance value is given. Ensure continuity exists between HO2S heater terminals.
2. Start engine and allow to idle until engine coolant temperature is 176°F (80°C) or more. Using fused jumper wires, carefully energize HO2S heater. Snap accelerate engine several times while measuring sensor output voltage. As air-fuel mixture becomes more rich, HO2S output voltage should be 0.6-1.0 volt. Replace HO2S if output voltage is not as specified. Recheck system proper operation.

Intake Air Temperature (IAT) Sensor

On all models except Eclipse 2.0L non-turbo and Mirage 1.5L, IAT sensor is a part of volume airflow sensor assembly. On all models, see appropriate SELF-DIAGNOSTICS article.

Manifold Absolute Pressure (MAP) Sensor

See appropriate SELF-DIAGNOSTICS article.

Manifold Differential Pressure (MDP) Sensor

See appropriate SELF-DIAGNOSTICS article.

Throttle Position (TP) Sensor (Eclipse 2.0L Turbo & 2.4L, Galant 2.4L & Montero Sport 2.4L)

1. Disconnect TP sensor connector. Check resistance between TP sensor connector terminals No. 1 and 4. Resistance should be 3500-6500 ohms.
2. While slowly opening throttle valve, check resistance between TP sensor connector terminals No. 2 and 4. Resistance should change smoothly in proportion to opening angle of throttle valve.

Vehicle Speed Sensor (VSS)

See appropriate SELF-DIAGNOSTICS article.

Volume Airflow Sensor

See appropriate SELF-DIAGNOSTICS article.

Automatic Transaxle/Transmission Range Switch Or Park Neutral Position Switch

See appropriate ELECTRONIC CONTROLS article in TRANSMISSIONS.

Closed Throttle Position Switch (Eclipse 2.0L Turbo & 2.4L & Montero Sport 2.4L, 3000GT)

Disconnect Throttle Position (TP) sensor connector. Check continuity between TP sensor connector terminals No. 3 and 4 with accelerator pedal depressed and released. When accelerator pedal is depressed, continuity should not exist. When accelerator pedal is released, continuity should exist.

Power Steering Oil Pressure (PSP) Switch

1. Disconnect pressure hose from oil pump. (Scheme 100) Install adapter on oil pump. Install adapter on disconnected hose. Connect pressure gauge and shutoff valve between adapters. Open shutoff valve. Bleed steering hydraulic system. See HYDRAULIC SYSTEM BLEEDING in appropriate article in STEERING.
2. Install a thermometer in fluid reservoir. Start engine and allow it to idle. Turn steering wheel several times until fluid temperature reaches 122-140°F (50-60°C). Disconnect PSP switch connector. Install a DVOM between ground and PSP switch terminal. (Scheme 100) Note continuity reading on DVOM. Go to next step.
3. With engine idling, gradually close shutoff valve to increase power steering system pressure. Check pressure when PSP switch is actuated by watching for a change in continuity. See «POWER STEERING SWITCH TEST PRESSURES»(ref-91126-S11026224302001030200000) table. Gradually open shutoff valve to decrease pressure. Check pressure when PSP switch is de-actuated. Turn engine off.

POWER STEERING SWITCH TEST PRESSURES

Scheme 100

Idle Air Control Motor

See appropriate IDLE AIR CONTROL (IAC) MOTOR under IDLE CONTROL SYSTEM.

ASD & Fuel Pump Relay (Eclipse 2.0L Non-Turbo)

Remove MFI (ASD) relay. Check resistance between relay terminals No. 4 and 6. Resistance should be 35-75 ohms. Connect jumper wire between battery positive terminal and relay terminal No. 6. Connect second jumper wire between battery negative terminal and MFI relay terminal No. 4. With relay energized, continuity should exist between terminals No. 2 and 8. With power source removed, continuity should not exist between terminals No. 2 and 8. If relay does not test as specified, replace MFI relay.

ASD, Fuel Pump & MFI Relay (All Except Eclipse 2.0L Non-Turbo)

Remove MFI/fuel pump relay. Check resistance between relay terminals No. 2 and 4. Resistance should be about 70 ohms. Connect jumper wire between battery positive terminal and relay terminal No. 4. Connect second jumper wire between battery negative terminal and MFI relay terminal No. 2. With relay energized, continuity should exist between terminals No. 1 and 3. With power source removed, continuity should not exist between terminals No. 1 and 3. If relay does not test as specified, replace MFI relay.

Radiator Cooling Fan Control Relay (High & Low)

See appropriate SELF-DIAGNOSTICS article.

EGR Solenoid Valve

See EXHAUST GAS RECIRCULATION (EGR) under EMISSION SYSTEMS & SUB-SYSTEMS.

EVAP Purge Solenoid Valve

See FUEL EVAPORATION under EMISSION SYSTEMS & SUB-SYSTEMS.

Fuel Pressure Solenoid (Turbo Models)

See TURBOCHARGER under AIR INDUCTION SYSTEMS.

Wastegate Control Solenoid Valve

See TURBOCHARGER under AIR INDUCTION SYSTEMS.

FUEL DELIVERY

Note. For fuel system pressure testing, see BASIC DIAGNOSTIC PROCEDURES article.

See TURBOCHARGER under AIR INDUCTION SYSTEMS.

Fuel Injectors

1. Listen to injectors during cranking and at idle. They should make ticking sound. Frequency of sound should increase as engine speed increases.
2. Except where noted, disconnect injector connector at injector. Check resistance between injector terminals. See «INJECTOR RESISTANCES»(ref-91126-S14810624242001030200000) table. For testing rear bank injectors on 3000GT, disconnect rear bank connector. Check resistance between terminals indicated in «3000GT REAR BANK INJECTOR CHECK»(ref-91126-S42122441452001030200000) table. For testing right bank injectors on Galant 3.0L, disconnect intermediate connector. Check resistance between terminals indicated in «GALANT RIGHT BANK INJECTOR CHECK»(ref-91126-S07541388572001030200000) table. For testing Montero 3.5L or Montero Sport 3.0L & 3.5L injectors, disconnect intermediate connector. Check resistance between intermediate connector terminals indicated in «MONTERO SPORT 3.0L & 3.5L INJECTOR CHECK»(ref-91126-S18693919112001030200000) table.

INJECTOR RESISTANCES

3000GT REAR BANK INJECTOR CHECK

GALANT RIGHT BANK INJECTOR CHECK

MONTERO & MONTERO SPORT 3.0L & 3.5L INJECTOR CHECK

3000GT (DOHC)

1. Turn ignition off. Disconnect ECM/PCM connector. See «POWERTRAIN CONTROL MODULE (ECM/PCM) LOCATION»(ref-91126-S24330683642001030200000) table under COMPUTERIZED ENGINE CONTROLS. Go to next step.
2. Turn headlights on. Measure voltage between ECM/PCM connector terminal No. 58 and chassis ground. If battery voltage is present, turn headlights off and go to next step. If battery voltage is not present, check and repair circuit between headlight relay connector and ECM/PCM connector.
3. Turn defogger switch on. Measure voltage between ECM/PCM connector terminal No. 58 and chassis ground. If battery voltage is present, turn defogger switch off and go to next step. If battery voltage is not present, check and repair circuit between defogger relay connector and ECM/PCM connector.
4. Depress brake pedal until brake lights come on. Measure voltage between ECM/PCM connector terminal No. 58 and chassis ground. If battery voltage is present, release brake pedal and go to next step. If battery voltage is not present, check and repair circuit between brake light relay connector and ECM/PCM connector.
5. If battery voltage is present and preceding tests do not show any system or component malfunction and ECM/PCM is suspected, substitute ECM/PCM with known-good unit and retest system.

Eclipse 2.0L Turbo & 2.4L & Montero Sport 2.4L & 3.0L

1. Engine coolant temperature must be 68°F (20°C) or less. If not, an Engine Coolant Temperature (ECT) sensor that is appropriate temperature can plugged into ECT sensor connector. Turn ignition on (engine off) and listen for IAC motor operation sound. Operational sound should be heard when ignition is turned on and off.
2. Disconnect IAC motor connector. Check resistance between IAC motor connector terminal No. 2 and either terminal No. 1 or 3. Also check resistance between IAC motor connector terminal No. 5 and either terminal No. 4 or 6. Each resistance at 68°F (20°C) should be 28-33 ohms.

Galant & Montero Sport 3.5L

1. Disconnect IAC motor connector. Check resistance between IAC motor connector terminal No. 2 and either terminal No. 1 or 3. Also check resistance between IAC motor connector terminal No. 5 and either terminal No. 4 or 6. Each resistance at 68°F (20°C) should be 28-33 ohms. If resistances are not as specified, replace IAC body assembly. If resistances are as specified, go to next step.
2. Remove IAC motor. Connect positive terminal of special tool 6 volt DC power supply to IAC motor connector (component side) terminals No. 2 and 5. (Scheme 101) Check for IAC motor vibration as negative terminal of 6 volt power supply is connected to each of following combinations of IAC motor connector terminals in sequence: Terminals No. 1 and 4. Terminals No. 3 and 4. Terminals No. 3 and 6. Terminals No. 1 and 6. Terminals No. 1 and 4. Terminals No. 1 and 6. Terminals No. 3 and 6. Terminals No. 3 and 4. Terminals No. 1 and 4. Vibration should be present at voltage application to each terminal combination. If IAC motor performs as specified, reinstall IAC motor and go to next step. If IAC motor does not perform as specified, replace IAC motor.

Scheme 101

IGNITION SYSTEM

Note. For basic ignition checks, see BASIC DIAGNOSTIC PROCEDURES article.

Camshaft Position Sensor

See appropriate SELF-DIAGNOSTICS article.

Crankshaft Position Sensor

See appropriate SELF-DIAGNOSTICS article.

Knock Sensor

See appropriate SELF-DIAGNOSTICS article.

EXHAUST GAS RECIRCULATION (EGR)

Note. To test EGR system or components not covered here, see appropriate SELF-DIAGNOSTICS article.

EGR System Check (Eclipse 2.0L Non-Turbo)

1. Start and warm engine to normal operating temperature. With transaxle in neutral and throttle closed, allow engine to idle 70 seconds. While watching stem of EGR valve, suddenly accelerate engine to 2000-3000 RPM. Stem should move when accelerating engine.
2. Remove and plug vacuum hose from EGR valve. Connect hand vacuum pump to EGR valve nipple. Apply 3.5 In. Hg (12 kPa) of vacuum to EGR valve. Engine should stall or idle become unstable.

EGR System Check (Eclipse 2.0L Turbo & 2.4L)

1. Engine should be cold (68°F (20°C) or less). Disconnect Green-striped vacuum hose (2.0L turbo) or White-striped vacuum hose (2.4L) from EGR solenoid valve. Connect hand vacuum pump to "T" fitting. Start engine. Check vacuum when engine is cold and engine is revved by quickly opening throttle. There should be no change in vacuum reading.
2. Warm up engine to 176°F (80°C) or less. Check vacuum when engine is warm and engine is revved by quickly opening throttle. Vacuum should momentarily rise over 3.9 in. Hg (13 kPa).
3. Disconnect hand vacuum pump from "T" fitting and connect directly to EGR valve. Apply 7.9 in. Hg (27 kPa) or more vacuum. Engine should stall or idle become unstable.

EGR System Check (Galant, Montero, Montero Sport & 3000GT)

1. Engine should be cold (68°F (20°C) or less). Connect "T" fitting in vacuum hose to EGR valve. Connect hand vacuum pump to "T" fitting. Start engine. Check vacuum when engine is cold and engine is revved by quickly opening throttle. There should be no change in vacuum reading.
2. Warm up engine to 176°F (80°C) or less. Check vacuum when engine is warm and engine is revved by quickly opening throttle. Vacuum should momentarily rise over 3.9 in. Hg (13 kPa).
3. Disconnect hand vacuum pump from "T" fitting and connect directly to EGR valve. On Galant or Montero Sport, apply 8.7 in. Hg (29 kPa) or more vacuum. On Montero or 3000GT, apply 9.1 in. Hg (31 kPa) or more vacuum. Engine should stall or idle become unstable.

EGR Solenoid Valve Check (Eclipse 2.0L Turbo)

1. Disconnect EGR solenoid electrical connector. Check resistance across EGR solenoid terminals. Resistance should be 62-74 ohms at 68°F (20°C).
2. Mark and disconnect vacuum hoses from EGR solenoid. Connect hand vacuum pump to EGR solenoid nipple furthest from terminal end of solenoid. Connect jumper wires between EGR solenoid terminals and battery positive terminal and battery negative terminal.
3. With jumper wires connected to battery, apply vacuum. Vacuum should leak. With battery voltage applied, plug nipple next to where vacuum hose is connected to. Then apply vacuum. Vacuum should hold. Disconnect battery voltage, unplug nipple and apply vacuum. Vacuum should hold.

EGR Solenoid Valve Check (Eclipse 2.4L)

1. Disconnect EGR solenoid electrical connector. Check resistance between EGR solenoid terminals. Resistance at 68°F (20°C) should be 62-74 ohms.
2. Label and disconnect vacuum hoses from EGR control solenoid valve. Using battery voltage and ground, energize control solenoid valve. Apply vacuum to vacuum nipple nearest terminals. Control solenoid valve should hold vacuum when energized, and release vacuum when battery voltage is removed. Replace EGR control solenoid as necessary.

EGR Solenoid Valve Check (Galant & Montero Sport)

1. Disconnect EGR solenoid electrical connector. Check resistance between EGR solenoid terminals. Resistance at 68°F (20°C) should be 36-44 ohms.
2. Label and disconnect vacuum hoses from EGR control solenoid valve. Using battery voltage and ground, energize control solenoid valve. Apply vacuum to vacuum nipple farthest from terminals. EGR solenoid valve should hold vacuum when energized and leak vacuum when battery voltage is removed.

EGR Valve Check (Eclipse 2.0L Non-Turbo)

1. Remove EGR valve and check for sticking, carbon deposits or other debris. Clean with suitable solvent as necessary and ensure valve seats properly.
2. Using a vacuum pump, apply 20 in. Hg (67 kPa) vacuum. Vacuum should hold. Apply 1.6 in. Hg (5 kPa) vacuum or less and blow into one EGR port. Air should blow out of other port. Then apply 8.7 in. Hg (29 kPa) vacuum or more and blow into one EGR port. Air should not blow out of other port.

Electric EGR Transducer Solenoid (Eclipse 2.0L Non-Turbo)

1. Disconnect EGR transducer solenoid electrical connectors. Check resistance between EGR transducer solenoid terminals. Resistance should be 25-35 ohms at 68°F (20°C).
2. Mark and disconnect vacuum hoses from EGR transducer solenoid. Plug nipple "A". (Scheme 102) Connect hand vacuum pump to nipple "B". Connect positive pressure-type hand pump to nipple "C". Connect jumper wires between EGR transducer solenoid terminals and battery positive and negative terminals.
3. Apply vacuum and note whether it holds or leaks while connecting and disconnecting, battery voltage and applying or not applying positive pressure. See «EGR TRANSDUCER SOLENOID TEST»(ref-91126-S13966285042001030200000) table. EGR TRANSDUCER SOLENOID TEST Jumper Wire Positive Pressure Status Vacuum Status Disconnected Not Applied Leaks Applied Holds Connected Not Applied Holds

Scheme 102

EVAP Control System Check (Eclipse, Galant & Montero Sport)

1. Make sure engine is at normal operating temperature. Disconnect purge hose from EVAP canister. Connect purge flow indicator (MB995061) between canister and purge hose.
2. Put transaxle in "N" or "P" range. Make sure lights, cooling fan and accessories are off. Run engine at idle for 3 or more minutes. While suddenly racing engine several times, check purge flow volume. Purge flow volume should be 20 cm 3 /sec (2.5 SCFH) or more. If purge flow is less than specified, retest with vacuum hose disconnected from canister. If purge flow is now as specified, replace canister. If purge flow is still less than specified, check vacuum port and vacuum hose for clogging.

Purge Solenoid Valve (PSV) (Eclipse 2.0L Non-Turbo)

1. Disconnect EVAP Purge Solenoid Valve (PSV) connector. Check resistance between PSV terminals. Resistance should be 27-37 ohms at 68°F (20°C).
2. Mark and disconnect vacuum hoses from PSV. Connect hand vacuum pump to bottom nipple on purge solenoid valve. Connect jumper wires between PSV terminals and battery positive and negative terminals. Apply vacuum and check for vacuum leaks while connecting and disconnecting battery. Vacuum should leak when voltage is applied. Vacuum should hold when voltage is removed.

Purge Solenoid Valve (PSV) (Eclipse 2.0L Turbo & 2.4L, Galant & Montero Sport)

1. Disconnect PSV electrical connector. Check resistance across PSV terminals. Resistance should be 36-44 ohms at 68°F (20°C).
2. Mark and disconnect vacuum hoses from PSV. Connect hand vacuum pump to PSV nipple furthest from terminal end of solenoid. Connect jumper wires between PSV terminals and battery positive terminal and battery negative terminal.
3. Apply vacuum with battery voltage applied. Vacuum should leak. Disconnect battery voltage and apply vacuum. Vacuum should hold.

Vent Solenoid Valve (VSV) (Eclipse 2.0L Non-Turbo)

Eclipse 2.0L non-turbo uses combined vent solenoid valve/leak detection pump. For diagnostics, see appropriate SELF-DIAGNOSTICS article.

Vent Solenoid Valve (VSV) (Eclipse 2.0L Turbo & 2.4L, Galant & Montero Sport)

1. Disconnect VSV electrical connector. Check resistance across PSV terminals. Resistance should be 17-21 ohms at 68°F (20°C).
2. Mark and disconnect vacuum hoses from VSV. Connect hand vacuum pump to PSV nipple closest to terminal end of solenoid. Connect jumper wires between PSV terminals and battery positive terminal and battery negative terminal.
3. Apply vacuum with battery voltage applied. Vacuum should hold. Disconnect battery voltage and apply vacuum. Vacuum should leak.

PCV Valve

1. Remove PCV valve and gently shake valve. Valve should rattle if moving freely.
2. Hold PCV valve with vacuum side down. Insert thin rod in top. Using light pressure, depress end of PCV valve spring .2-.3" (5-10 mm). Release pressure on rod. PCV valve spring should quickly lift rod to its original position.
3. Connect PCV valve to vacuum hose, and start engine. Ensure vacuum is flowing through valve. Clean or replace PCV valve as necessary.

MISCELLANEOUS CONTROLS

Note. Although the controlled devices listed here are not technically engine performance components, they can affect driveability if they malfunction.

Note. To identify ECM/PCM A/C power supply voltage terminals, see appropriate pin voltage chart in PIN VOLTAGE CHARTS article. To identify ECM/PCM A/C power supply circuit, see appropriate wiring diagram in WIRING DIAGRAMS article.

A/C Switch & Compressor Clutch Relay

Using DVOM, check A/C power supply voltage from ECM/PCM. Turn ignition switch to OFF position. Disconnect ECM/PCM connector. Turn A/C switch and ignition switch to ON position. Measure voltage between ECM/PCM A/C power supply terminal and chassis ground. If battery voltage is not as present, check and repair circuit(s).