Description

Chrysler NS, GS Service Manual – Emission Control Systems

Got a Chrysler NS or GS with a check engine light that won’t go out? You’ve been chasing a DTC 43 misfire code for two weekends. The parts store sold you an oxygen sensor you didn’t need. I’ve seen it a hundred times. Stop throwing parts at it. Use the factory document that spells out exactly what the PCM needs to see before it sets a code. This 38-page Chrysler NS, GS Service Manual is a direct OEM scan of the emission control section—no aftermarket rewrites, no vague diagrams. It came off a Chrysler tech’s bench, and it belongs on yours.

Emission Control Systems: What This Manual Covers

The manual is split into three main chapters: ON-BOARD DIAGNOSTICS (page 1), EVAPORATIVE EMISSION CONTROLS (page 14), and EXHAUST GAS RECIRCULATION (EGR) SYSTEM (page 22). That’s the entire emissions picture for NS and GS models. You get the factory logic for how the PCM decides to store a DTC, including the specific RPM and temperature thresholds. For example, the OBD section explains that if a sensor shorts to ground above 2400 RPM but the monitor window is 750–2000 RPM, the PCM won’t set a code. That kind of detail keeps you from chasing ghosts. The EVAP section covers the duty cycle purge solenoid, leak detection pump, and pressure‑vacuum filler cap. The EGR chapter walks through the 3.0L and 3.3/3.8L valve and tube services with removal and installation steps.

On-Board Diagnostics and DTC Retrieval

First thing you need to know: this manual lists every monitored system and the conditions that trigger a code. Monitored systems include oxygen sensors (DTC 21, HEX 66/7A), fuel system monitor (DTC 51/52), EGR monitor (DTC 32), catalyst monitor (DTC 64), misfire monitor (DTC 43), and leak detection pump (DTC 31). There’s a full DTC description table cross‑referenced with HEX values. To retrieve codes, you have two options: use a DRB scan tool or read the MIL lamp flashes. The manual shows the exact procedure for both, including circuit actuation test mode. Don’t have a DRB? Page 3 of the OBD section (inside the 38 pages) tells you how to get codes from the lamp. If you’re working on a 2.5L diesel, flip to the addendum—it has a separate DTC access method and a torque chart. For wiring details, pair this with the Chrysler NS GS Wiring Diagram.

Does It Cover the EVAP System?

Yes, and it doesn’t skip the leak detection pump. The EVAP section includes diagnosis and testing procedures for the pump, PCV valve, and vacuum schematics. You’ll find removal and installation steps for the leak detection pump—one of the most misdiagnosed components on these cars. The manual also covers the pressure‑vacuum filler cap and the duty cycle canister purge solenoid. If you’re dealing with a P0442 small leak, this is where you start. For related drivetrain work, check the Chrysler NS/GS Transaxle and Power Transfer Unit Service Manual – Section: Power if you need to drop the subframe for EVAP line access.

Get the Right Torque Specs for the EGR System

The EGR chapter has dedicated torque charts for the 2.5L diesel, 3.0L, and 3.3/3.8L engines. Over‑torquing the EGR tube nuts will warp the flange—I’ve seen it. The manual gives you the numbers: for the 3.0L valve, tighten to 20 ft‑lbs; for the 3.3/3.8L, it’s 40 in‑lbs. And don’t skip the EGR valve control (transducer) test. The manual has a two‑part procedure: test the electrical solenoid portion first, then the vacuum transducer portion. If you’re swapping a transaxle, you’ll need the Chrysler NS GS Tires & Wheels Service Manual for alignment specs after reassembly.

Why OEM Documentation Beats Aftermarket

I’ve seen third‑party manuals round TORQUE values to the nearest 5 ft‑lbs. That’s how you snap bolts. This is a direct factory scan from Chrysler—same document a dealer tech pulls up on the DRB. The 38 pages include the exact PCM logic, vacuum schematics, and component monitor criteria. No interpretations, no errors. If you need background on how a Manual Transmission works in relation to the PCM’s load calculation, check the external resource—but for emissions diagnostics, this OEM manual is the final word. For a visual walkthrough of the EGR flow test, this Manual Transmission video uses the same factory procedure.

3 Common Emission Problems Addressed

DTC 43 misfire, DTC 32 EGR insufficient flow, and DTC 31 leak detection pump failure. The manual gives you the diagnostic tree for each. For misfire, it lists secondary ignition circuit checks, cylinder compression, and fuel injector mechanical malfunctions. For EGR, there’s a gas flow test and a leakage test. For the LDP, there’s a full electrical and vacuum test plus replacement instructions. You also get the non‑monitored circuits list—stuff the PCM ignores—so you don’t waste time testing circuits that won’t trigger a code.

FAQ

Does this manual cover the 2.5L diesel engine?

Yes, the addendum includes system description, DTC access, and a torque chart specific to the 2.5L diesel.

Can I use this manual to diagnose a P0420 catalyst efficiency code?

It covers the catalyst monitor (DTC 64 Hex 70/B4). The manual explains that the PCM compares upstream and downstream O2 sensor activity to determine catalyst efficiency. It won’t give you a step-by-step beyond monitor criteria, but you’ll understand why the code set.

What tools do I need for the EGR valve test?

You need a hand vacuum pump, a multimeter, and a DRB scan tool (or MIL lamp access). The electrical solenoid portion requires an ohmmeter to check coil resistance; the transducer portion requires a vacuum pump to test diaphragm integrity. The manual lists special tools: the Chrysler EGR adapter and a tachometer for the gas flow test.

How do I obtain DTCs without a DRB scan tool?

Turn the ignition key on-off-on-off-on within 5 seconds. The MIL will flash the trouble codes as two-digit sequences (e.g., flash-pause-flash-flash = code 12). Write them down and cross-reference with the DTC chart in the manual. This works on all NS/GS models covered.

Access the Factory Manual now and put the right information on your bench. No more reprints, no aftermarket guesswork—just the original Chrysler service data that keeps your emission controls working as designed.