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97 Jeep Grand Cherokee Laredo 4.0L Persistent P0201-P0206 Injector Control Codes: Diagnosis and Fixes

Model: 97 jeep grand cherokee laredo 4.0L Fault Code: P0201 Posted: 2021-05-10 09:19

We recently rebuilt a 97 Jeep Grand Cherokee Laredo 4.0L engine after a blown motor, sourcing it from a junkyard. The vehicle sat for nearly two years before restoration began. After initial startup, the engine ran extremely rough and would die when an O2 sensor was plugged in—no restart or code reader connection possible. We replaced the original PCM with one purchased from Car Computer Exchange ($200), which allowed the engine to run but with a noticeably poor performance. This is when we discovered persistent P0201 through P0206 injector control circuit codes. Extensive troubleshooting has been performed: relays, wiring harnesses (including a new one from a junkyard), fuel injectors, distributor, O2 sensors, catalytic converter, alternator, engine coolant temperature sensor (ECTS), and TSP. Despite these changes, the P0201-P0206 codes persist. An interesting observation: even after replacing the ECTS, the central control module still reports it as 'bad.' When disconnected, a P0118 code appears. Voltage readings on the sensor show 5.13V—above the typical threshold of 4.9V. Some sources suggest that any reading above 4.9V triggers multiple codes. We have intermittent fault codes including manifold pressure issues and O2 sensor-related errors. A full list will be shared once compiled. The current setup includes a basic Harbor Freight code reader (with freeze frame data) and a more advanced scan tool for live data. We are now focused on diagnosing the injector control circuits to determine if wiring, power delivery, or PCM compatibility is at fault.

Related fault codes

P0201P0202P0203P0204P0205P0206

Comments (16)

Anonymous 2021-05-10 09:23

The user has adjusted timing and rocker arms to factory specifications. However, confusion remains regarding the correct firing order due to conflicting information online.

Anonymous 2021-05-10 14:21

I just checked the fuel injector connectors—no power detected on Injector #2. What should I do next, George? LOL

Anonymous 2021-05-11 07:41

Timing is typically managed by the PCM and not manually adjustable. To assist further, I recommend using TP pins available at Walmart to back-probe connectors along with a DC voltmeter. What codes appear after clearing the memory? Injector control circuit faults can damage the catalytic converter—did you see these codes on the original PCM? Was the new PCM flashed with the vehicle’s VIN?

Anonymous 2021-05-11 07:43

A reading of 5.13V on an unplugged ECTS is normal; unplugging it should trigger a P0118 code, which confirms proper sensor behavior.

Anonymous 2021-05-11 07:43

Do you have access to a code reader or scan tool? The Harbor Freight model has freeze frame data and can provide basic diagnostics. I’ve borrowed a more advanced tool for live data monitoring.

Anonymous 2021-05-12 06:34

I have a multimeter—can it handle DC voltage and resistance testing? I’ll pick up TP pins this morning. What codes appear after clearing? -All P0201 through P0206 codes, appearing only when attempting to start. Did you see injector control codes on the original PCM? I believe not—though I’m unsure. Before swapping the wiring harness, it showed 'injector 1 circuit open.' After the harness change, it became 'injector circuit/cylinder open.' Was the new PCM flashed with VIN? Yes—but would a 98 motor swap affect this? I can’t recall the original year of the engine. However, 97 and 98 models are generally interchangeable in terms of mounting and alignment.

Anonymous 2021-05-12 06:38

Do you have a code reader or scan tool? Yes—Harbor Freight model with freeze frame data. I’ve borrowed a more advanced one for live data, which I may use again.

Anonymous 2021-05-12 07:01

Are all P0201–P0206 injector control codes present? Yes—initially. However, if the engine idles briefly, additional codes such as loss of cam/crankshaft or O2 sensor issues may appear. I have TP pins now. First, disconnect each injector connector: use the multimeter’s positive probe on the injector feed wire and negative to battery ground. Test for 12V when turning the key to 'on' position (for a few seconds)—the ASD relay provides brief power during this phase. All feed wires should be dark green/orange. Let me know results. A test light is also recommended.

Anonymous 2021-05-12 07:36

After testing, clear the codes before proceeding to the next step.

Anonymous 2021-05-12 11:29

All P0201–P0206 codes initially. But after a brief idle, other codes appear—such as loss of cam/crankshaft and O2 sensor faults. I’ll share the full list soon. I have TP pins now. Test procedure: - Disconnect each injector connector. - Use multimeter: positive to feed wire, negative to battery ground. - Test for 12V when key is turned 'on' (a few seconds). - All wires tested—positive result. - Feed wires are dark green/orange as expected. - I have a test light now. [Note: All tests completed successfully.]

Anonymous 2021-05-12 18:20

Now perform injector control circuit testing. Clear codes before each test. For each injector: - Disconnect the connector. - Use a test light connected to battery positive, touch the control wire on the connector (not dark green/orange). - The test light should flicker when cranking. A noid light can also be used for confirmation. Test one at a time and plug back in between tests after clearing codes. Report results.

Anonymous 2021-05-12 18:45

Test one injector at a time, re-plugging the connector before moving to the next. Clear codes after each test.

Anonymous 2021-05-12 22:16

Exciting progress! Here are the results: #1: Turn key—flicker; start—flash; codes clear. #2: Turn key—no flicker; start—no response; codes show P0204, P0205, P0206. #3: Turn key—flicker; start—flash; codes clear. #4 (retested): Turn key—flicker; start—flash; codes show P0201, P0202. #5: Turn key—no flicker; start—no response; codes show P0201, P0202. #6: Turn key—no power; start—no response; codes show P0201, P0203. Redid #4: Turn key—no power; start—no response; codes show P0201, P0203. This indicates a potential issue with injectors 2 and 5–6.

Anonymous 2021-05-13 07:01

Injector #4 (cylinder 4) shows no flicker from the test light. Back-probe the injector control wire that did not show flicker while connected—use a multimeter: negative to battery ground, positive to TP pin on the back-probed control wire. Crank the engine—should see 12V. If not, further testing with PCM pinout and meter is required. I need access to the PCM pinout diagram for accurate wiring reference.

Anonymous 2021-05-13 19:29

Clarification: For Injector #4 (cylinder 4), no flicker from test light when connector was plugged in. Back-probe the control wire that showed no flicker. Connect multimeter negative to battery ground, positive to TP pin on the back-probed control wire. Crank engine—should see 12V. If not, additional testing with a meter and PCM pinout is needed. I already have access to the PCM wiring diagram.

Anonymous 2021-05-14 07:38

For each injector, disconnect the connector and use a test light connected to battery positive—touch the control wire while cranking. The test light should flicker. Repeat for all injectors to identify which one has an open or faulty control circuit.