Ect Wiring Diagram 1998 Ls1

Production GM vehicles rely on the PCM to provide signal outputs to control the engine, gauges, electric fans, emissions equipment, air conditioning, and other equipment.s

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Production GM vehicles rely on the PCM to provide signal outputs to control the engine, gauges, electric fans, emissions equipment, air conditioning, and other equipment.s

Engine Control Output

The basic purpose of any engine computer is to correctly deliver fuel and initiate ignition events for any engine operating condition. To do this correctly, engines are fitted with many sensors that provide measurable real-time operating data. Combined with calibrated parameters, the sensor values are used by the engine computer to activate the injector and ignition-coil control signals.

LS-series ignition coils are interchangeable. As an example, you can swap a 2002 Corvette ignition coil bracket assembly (ignition coils, mounting bracket, and coil harness) with a 2008 Corvette ignition coil bracket assembly. General Motors has designed each ignition coil pack harness to be universal to any LS-series engine wire harness. General Motors has used a variety of ignition coils with LS-series engines. GM# 12558948 ignition coil (bottom left) is only used with the LS1 and LS6 engine in the Camaro, Firebird, Corvette, and Cadillac CTS-V. GM# 12573190 ignition coil (middle left) and GM# 12611424 ignition coil (top left) are used with 2005-newer cars, trucks, and vans. GM# 10457730 ignition coil (bottom right) and GM# 12558693 (top right) are used with
1999–2007 trucks and vans.

Ignition Coils

All Gen III engines are fitted with eight ignition coils. Each coil is responsible for delivering spark to its assigned cylinder. The engine computer must determine spark angle, or degrees Before Top Dead Center (BTDC), to activate each ignition coil through the ignition control (IC) circuit. As part of this complicated calculation, the engine computer considers engine speed (CKP input), coolant temperature (ECT input), intake air temperature (IAT input), knock sensor values (KS input), throttle position (TPS input), vehicle speed (VSS input), transmission gear (P/N input), and more. To prevent weak spark, the engine computer also controls the ignition coil charge time (or dwell time) before firing. (See Figure 6.1.)

LS-Series Ignition Coil Output LS-series engines have eight individual coils. To release a coil's charge when an ignition event is requested, the engine computer commands the IC coil output circuit low (toward 0V). This energizes the ignition coil and causes the spark plug to produce spark. All ignition coils on LS-series engines operate in the same way. Changing a set of eight ignition coils for a different set of eight ignition coils may require (or at the very least, benefit from) changes to the engine computer's spark calibration, including the spark dwell time table. (See Figure 6.1.)

Fig. 6.1. This table represents lookup values for the amount of time the ignition coils are charged before the PCM sends a signal to fire them. If the dwell time is too long, the ignition coils may overheat. If the dwell time is too short, a weak spark (and loss of power) may result.

This LS1 and LS6 GM coil bracket assembly is installed on all 1999-newer LS1 and LS6 engine valve covers. A coil bracket assembly includes a formed steel bracket, four ignition coils, and a wire harness. With a variety of LS-series ignition coils, not all coil mounting positions and brackets are the same. However, General Motors has designed all coil pack wire harnesses to universally plug into any LS-series engine wire harness.

EFI Connection offers a coil bracket assembly that uses GM# 12573190 ignition coils. The coil bracket cleanly fits Gen I small-block and Gen II LT1 engine center bolt valve covers. The layout allows clearance for oil fill, PCV, and breather. The wire harness is specific to the bracket and ignition coil layout, but universally plugs into any LS-series engine wire harness. For engines with perimeter-bolt valve covers, bosses can be welded to the surface of the valve cover for attachment.

Since 1996, the Vortec V-6 and Vortec V-8 engines have used a single coil, ignition module, and distributor. The 2001–2002 GM vehicles with Vortec V-6 and Vortec V-8 engines use the same PCM (GM# 12200411) as the vehicles with LS-series engines. Engine operation requires a four-pulse (for V-8) crankshaft signal (reluctor and sensor at bottom), one-pulse camshaft signal from within a Vortec distributor (right), a single coil and ignition module (middle), GM# 12200411 PCM (left), and a base PCM calibration that supports a low-resolution crankshaft signal with single coil and distributor (like a 2001 5.7L Express Van calibration). Vortec V-6 engines require a three-pulse crankshaft signal and supporting PCM calibration (like a 2001 4.3L S-10 calibration).

Fig. 6.2. The V-8 and V-6 Vortec ignition system components have remained unchanged since 1996. All 1996-newer Vortec V-8 and V-6 engines use the same ignition module, ignition coil, CKP sensor, and CMP sensor. Due to the variations in engine size, and for accuracy, several different knock sensors have been used. Because only the PCM has been changed throughout the years, the 2001-2002 Gen III PCM (GM# 12200411) may be used with any 1996-newer V-8 and V-6 Vortec engine.

Vortec V-6 and Gen I Small-Block Vortec V-8 Ignition Coil Output: The only Gen III PCM that General Motors used with the Vortec V-6 and Gen I small-block Vortec V-8 engines is the 2001–2002 (GM# 12200411). These engines only offer single coil and distributor ignition. Comparing wire schematics between an LS-series engine and Vortec V-6 or Vortec V-8 engine reveals that the same IC circuit controlling ignition coil 1 on the LS-series engines is used to control the ignition control module (ICM) of the Vortec V-6 and Gen I small-block Vortec V-8 engines. (See Figure 6.2.) The ICM causes the ignition coil to fire based on IC circuit signal pulses.

Fuel Injector Control

By 1996 all GM V-6 and V-8 engines were fitted with one injector for each cylinder. The engine computer controls each fuel injector through an internal switch (or driver), which applies a ground signal to each fuel injector. With 12V ignition power at each injector while the engine is running, the fuel injector driver applies ground, opening each injector to allow fuel to pass through the injector and into the engine cylinder The engine computer controls the pulse width (or duration) and sequencing of each injector driver. The engine computer determines fuel injector sequencing based on crankshaft position (CKP) and camshaft position (CMP). Pulse widths are calculated from inputs such as air mass (MAF input), manifold pressure (MAP input), throttle position (TPS input), intake air temperature (IAT input), coolant temperature (ECT input), engine speed (CKP input), and more.

The firing order is hardwired to the engine computer, but the bank assignment of each injector is defined within the engine computer's calibration. (See Chapter 7 for more about the firing order.)

Fuel Pump Relay Control

The fuel pump is controlled by the engine computer through a relay. The relay coil is grounded and the engine computer supplies a 12V power source to the relay coil. This switches battery power to the fuel pump. When the ignition switch is turned to the ON position, the PCM cycles the fuel pump on for several seconds to pressurize the fuel rails. The fuel pump only runs when the engine computer sees a signal from the CKP sensor indicating that the crankshaft is rotating.

The fuel pump is turned on through a relay because the PCM cannot handle the current. When the ignition key is turned on, the PCM turns the fuel pump relay on for several seconds to prime the fuel system. The PCM does not command the fuel pump to run again until a signal is received from the CKP sensor.

The PCM controls the illumination of the MIL by applying a ground to the bulb. Ignition power is received at the bulb from the gauges fuse. The MIL is important because it may be the first indicator
that there is a problem with engine or transmission performance.

The PCM uses the VSS and calibration data to determine how many pulses to output for each of the VSS outputs. Most production GM vehicles only use the primary VSS output, which is most often used for the speedometer. The secondary VSS output, for example, can be used with any third generation F-Body to satisfy the 2,000-pulse-per-mile cruise control module VSS signal input requirement.

The PCM calculates engine speed(RPM) based on the signal it receives from the CKP sensor. The RPM signal is then output to the tachometer.

Malfunction Indicator Lamp Control

Knowing that a malfunction is occurring (or has occurred) can be critical. The malfunction indicator lamp (MIL) in the instrument cluster is used to indicate that a malfunction has occurred. In a production GM vehicle, the MIL receives 12V power through the gauges fuse. The engine computer applies a ground to. the control circuit to illuminate the lamp. When the cause of a malfunction has been fixed, the MIL can be reset by clearing stored DTCs or by running the engine or transmission through several cycles as defined in the calibration.

Tachometer Output

The engine computer provides a tachometer output for monitoring engine speed. For LS-series engines, one revolution per minute (RPM) equals one set of 24 crankshaft signal pulses. For Gen I small-block Vortec and Gen VI big-block Vortec engines, one rpm equals one set of four crankshaft signal pulses. For Vortec V-6 engines, one rpm equals one set of three crankshaft signal pulses. The engine computer calibration allows for adjustment to the output signal for compatibility with many tachometers.

The number of output pulses for the tachometer is configurable. As shown here, the tachometer in a 2002 LS1 Camaro instrument cluster requires the Tacho Pulses High and Tacho Pulses Low values of "6." As another example, a Gen III PCM installation into an LT1 Camaro requires Tacho Pulses High and Tacho Pulses Low values of "3" and Tacho Pullup Enable set to "Yes."

Vehicle Speed Output

Two VSS outputs are available with Gen III PCMs. These VSS outputs are defined in the PCM calibration as primary and secondary. For production GM vehicles, the primary VSS output is often used for the speedometer and the secondary VSS output is often used for the antilock brake system (ABS). The pulse count for each VSS output is configurable within the PCM calibration.

Electric Fan Control

While all Gen III PCMs support electric fan control, not all production GM vehicles with a Gen III PCM have electric fans. The PCM controls two output signals based on coolant temperature (ECT input), vehicle speed (VSS input), and air conditioning inputs. General Motors uses these two outputs with three relays to operate two electric fans in low/ high-speed operation by switching between series and parallel operation. (See Chapter 11 for more information about electric fan operation.)

Using EFILive, from Calibration > Speedometer > Parameters, you find the primary VSS output (calibration {H0105}) and the secondary VSS output (calibration {H0106}). These values should be set after the VSS tooth count, tire size, and gear ratio have been properly set in the PCM calibration file.

EFILive's Speedo Calculator is accessed from Calibrations > Speedometer > Parameters > Speedo Calculator. The Speedo Calculator tab presents tire size, gear ratio, and number of teeth on the VSS pickup reluctor. The Sprocket Ratios tab is related to front-wheel- drive transmissions. The Speedo Fine Tuning tab is most accurately used while the vehicle is on a chassis dyno to make fine adjustments to the value displayed on the speedometer. The Shift Point Correction tab allows a percentage adjustment to the shift tables after a tire size or gear ratio change.

Air Conditioning Control

The PCM is solely responsible for controlling the A/C compressor clutch through a relay. The A/C compressor clutch relay coil and switch receive 12V ignition power with the key in the ON position. Based on the A/C request input, A/C compressor clutch supply voltage input, A/C pressure sensor input, engine speed (RPM input), throttle angle (TPS input), and intake air temperature (IAT input), the PCM applies a ground to the control circuit to switch 12V power to the A/C compressor clutch. (See Chapter 11 for more information about A/C operation.)

Generator Control

Gen III PCMs have the ability to control generator load on the engine through a turn-on signal output. In addition, some vehicles use a generator field duty cycle signal input to the PCM to monitor the duty cycle (ON/OFF) of the generator. Generator load on the engine is calculated based on a PWM signal from the generator. Many conversions disable PCM generator control, but it may be beneficial to retain or enable this feature to adjust engine idle speed to compensate for high generator loads.

Production vehicles with Gen III PCMs use the PCM to control the generator. Although the generator turn-on signal output is always used, the generator field duty cycle signal is not. Most commonly the Camaro and Firebird use only the generator turn-on signal; trucks and vans use both the generator turn-on signal and the generator field duty cycle signal; the Corvette uses both PCM signals plus a 16-gauge battery wire (in generator connector cavity A). Be sure to consider which generator you are working with and your instrument panel charge lamp requirement when wiring your generator.

When the PCM is not used to control the generator, there are a few DTCs that need to be disabled. There are two parts to disabling these DTCs: processing enablers and MIL enablers. By setting DTCs P1637 and P1638 to "Not Reported" within the processing enablers, the PCM ignores the processing of these DTCs.

By setting DTCs P1637 and P1638 to "No MIL" within the MIL enablers, the PCM does not apply ground to the MIL control circuit (the MIL does not illuminate).

Although the PCM is capable of controlling AIR, EGR, and EVAP, using the PCMs emissions controls does not necessarily mean emissions compliance in your state or county. Before removing emissions equipment, check with your local emissions laws. Removing emissions components also requires turning off (or disabling) the DTC processing enablers and DTC MIL enablers within the PCM calibration.

When the PCM is not used to control the generator, DTCs P1637 and P1638 need to be disabled. If you forget to disable these DTCs, they appear in the list of active DTCs when you scan the PCM through the DLC.

Emissions Control

Gen III PCMs are emissions control capable, but may not be emissions compliant. Your state has specific emissions laws for on-road vehicles that you must adhere to for emissions compliance. After checking with your local emissions testing station, you may find that emissions compliance for your conversion simply means adding a charcoal canister and purge line, or you may find that emissions compliance requires all relevant emissions control of your engine's original vehicle.

EVAP Canister Purge Solenoid

Today's vehicles are equipped with an evaporative emissions (EVAP) control system. Its primary function is to control a charcoal canister purge solenoid. This canister stores fuel vapor and is connected to the fuel tank through a hose.

The engine computer controls the purge solenoid during engine operation to purge the charcoal canister of fuel vapor. Intake manifold vacuum pulls the fuel vapor from the charcoal canister so it can be burned in the combustion process. The PCM applies logic to the operation of the purge solenoid so the purge routine does not create a rich or lean condition.

The PCM checks EVAP purge solenoid performance by monitoring fuel tank pressure (or vacuum) through the fuel tank pressure sensor. If fuel tank vacuum is more than expected within a predetermined amount of time, the PCM knows that the EVAP purge solenoid is leaking engine vacuum to the fuel tank and sets a DTC.

EVAP Canister Vent Solenoid

The EVAP vent valve allows fresh air to enter the EVAP canister. The vent valve is normally open, but is closed when the PCM-controlled vent solenoid is activated. Closing the vent valve allows the PCM to test the EVAP lines for any leaks. To activate the vent solenoid, the PCM applies a ground.

EGR Solenoid Control and Valve Position Signal

The exhaust gas recirculation (EGR) valve introduces exhaust into the intake manifold to be burned in the combustion process, effectively lowering exhaust temperatures by diluting the air/fuel mixture. Because high exhaust temperatures generate nitrogen (NOx) emissions, the effect is lower levels of NOx. Production LS-series engines without an EGR valve perform an EGR function through the camshaft profile with valve timing that accomplishes a similar effect.

The EGR valves used with the Gen III PCM are unlike the early vacuumoperated EGR valves. The LT1 EGR valve (left) opens when vacuum is applied through the electrical solenoid. (Notice the vacuum lines from the solenoid to the engine and from the solenoid to the EGR valve assembly.) Newer engines use an electronically controlled EGR valve (right) with an internal sensor. Early engines being converted for Gen III PCM use either need a custom EGR solution or the elimination of the EGR valve.

Skip shift calibration options can be found in EFILive through Transmission Calibration > CARS/CAGS > Parameters.

The PCM supplies a 5V reference and ground to the EGR solenoid to open and close the valve through a PWM signal. EGR valve position is monitored by the PCM through a sensor within the EGR valve assembly. The PCM runs diagnostic tests to determine if the valve is operating as it is commanded.

AIR Pump Control

Secondary air injection (referred to as AIR, an acronym for "air injection reactor") is a method of injecting fresh air into the exhaust stream. A similar method was implemented before electronic fuel injection as a means of lowering emissions through a more complete combustion of exhaust gases.

With the addition of the catalytic converter and modern PCM logic, the AIR system now serves the purpose of injecting fresh air into the exhaust steam during cold starts to effectively raise the exhaust temperatures at the catalytic converter, bringing the converter up to temperature faster for efficient burn of otherwise rich exhaust mixture. During normal engine operating temperatures, the AIR system continues to serve the purpose of reducing carbon monoxide (CO) and hydrocarbons (HC) emissions.

The electronic AIR pump is controlled by the PCM through a relay. The AIR pump relay coil and switch receive 12V battery power through a fused source. When the PCM applies a ground to the relay coil, the relay routes 12V to the AIR pump and fresh air is then introduced into the exhaust manifolds.

Skip Shift Solenoid Control

Vehicles with 6-speed manual transmissions (T56 transmissions) have a feature called skip shift (or computer-aided ratio selection, CARS). It improves fuel economy by using a PCM-controlled solenoid to block out second and third gear during certain driving conditions. The PCM applies a ground to this control circuit to energize the solenoid. An increase in throttle angle or vehicle speed is required to deactivate the solenoid. Many conversions disable this feature. Devices to eliminate skip shift are available, but a simpler solution is to disable the feature in the calibration.

If disabling skip shift (and/or reverse lockout), also be sure to disable DTC processing in the engine diagnostics section of the PCM calibration. By setting DTCs P0801, P0803, and P0804 to "Not Reported" within the processing enablers, the PCM ignores the processing of these DTCs.

Reverse-Inhibit Solenoid Control

Vehicles with 6-speed manual transmissions contain a reverse-inhibit (or reverse lockout) feature that prevents the driver from (accidentally) shifting into reverse when the vehicle is in motion. The PCM energizes the reverse-inhibit solenoid by applying a ground. With the solenoid energized, the driver can shift the transmission into reverse. When the PCM removes ground from the solenoid, the solenoid is deactivated and the driver is prevented from shifting into reverse.

If disabling skip shift (and/or reverse lockout), also be sure to disable MIL illumination in the engine diagnostics section of the PCM calibration. By setting DTCs P0801, P0803, and P0804 to "No MIL" within the MIL enablers, the PCM does not apply ground to the MIL control circuit (the MIL does not illuminate).

The Gen III PCMs are capable of controlling the skip shift and reverse-lockout solenoids found on the T56 6-speed manual transmission (Camaro, Firebird, and Corvette). PCM control of these solenoids can be enabled or disabled within the PCM calibration.

Transmission Control

All Gen III PCMs were used with 4L60-E transmissions. If your project includes a 4L60-E transmission, you can choose any Gen III PCM for 4L60-E control.) GM trucks and vans were the only vehicles to receive 4L80-E transmissions. Because the Gen III PCM was only used with 1999-newer trucks and vans, the 1997–1998 Gen III

PCM does not directly support 4L80-E transmissions. If your project includes a 4L80-E transmission, choose any 1999-newer Gen III PCM for 4L80-E control. (See Chapter 10 for more information on transmissions.)

Serial Data Output

Gen III PCMs have two Class 2 serial data outputs. In most production vehicles with a Gen III PCM, pin 58 of the PCM's blue connector is used for Class 2 serial data communication. For conversions, this wire is used by the OBD-II DLC. (See Chapter 14 for more information about OBD-II.)

For use with electronic throttle systems only, the PCM has two discrete (meaning one source and one destination) universal asynchronous receiver-transmitter (UART) communication circuits for data transfer between the PCM and TAC module.(See Chapter 8 for more about electronic throttle systems.)

Written by Mike Noonan and Posted with Permission of CarTechBooks

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