← Back to list

2004 Chevy Cavalier 2.2L Ecotec C1236 Fault Code: Diagnosis & Starting Issues

Model: 2004 Chevy Cavalier Fault Code: C1236 Posted: 2014-03-26 12:27

I've thoroughly checked fuel pressure, compression, and ignition components, but the only remaining possibilities are the crankshaft position sensor or powertrain control module (PCM). I've replaced three different ECUs with no success. The car will start for a brief moment when starting fluid is sprayed into the intake manifold, then immediately dies. Initially, symptoms were sporadic idle issues that eventually led to complete stalling. The fault code displayed is C1236 — indicating low system supply voltage — along with other related codes such as C1275 (Powertrain Control Module ETS disconnected), P0507 (Idle Air Control system RPM higher than expected), and multiple injector circuit open faults (P0201, P0202, P0203, P0204). Fuel pressure readings show 40 psi with the key off, rising to between 50–60 psi when the key is turned on. Despite this, the engine fails to start reliably. I have not yet tested the injectors using a Noid light. If the injector signal wire remains grounded during cranking, it could cause continuous fuel delivery and flooding — which may explain why the engine starts briefly with starting fluid but dies immediately afterward. I've also noticed that the engine oil appears thicker than normal and has a gasoline odor, raising concerns about potential fuel leaks or internal system failure. Given that the car ran normally for 112 miles before exhibiting issues, and the security light is not illuminated, I'm leaning away from a security-related fault. However, the intermittent starting behavior and persistent C1236 code suggest a deeper issue involving either the PCM, fuel delivery system, or sensor inputs — particularly the crankshaft position sensor. Since the Noid light does not flash during cranking, this further supports the possibility of an injector circuit malfunction or faulty signal wiring. What could be causing these symptoms? Is C1236 directly related to the inability to start, or is it a secondary symptom of another underlying problem?

Related fault codes

C1236

Comments (10)

Anonymous 2014-03-26 12:41

What is your fuel pressure reading? (in psi) Did you test the injectors with a Noid light? Is there any other warning light on — such as security or ABS? Is the only fault code a 'C' code? Note: C codes typically relate to powertrain system faults, not directly to starting issues.

Anonymous 2014-03-26 12:47

C1236 indicates low system supply voltage; C1275 suggests the Powertrain Control Module (PCM) is disconnected from the ETS. P0507 points to an idle air control issue — I replaced the IAC valve. P0201–P0204 indicate open injector circuits. Fuel pressure: 40 psi with key off, rising to 50–60 psi with key on. Does this mean C codes are unrelated to starting? Or could they be symptoms of a deeper system failure?

Anonymous 2014-03-26 12:59

There are 22 total fault codes. Only P-codes present are P0507 and P0201, P0203, P0204 (injector circuits open). I have not yet tested the injectors with a Noid light. If the Noid light remains on during cranking, what does that indicate? Could it point to a stuck-open injector?

Anonymous 2014-03-26 13:03

What is your fuel pressure in psi? Is the security warning light on (if applicable)? The Noid light should flash during engine cranking. There are three possible states: 1. Light stays steadily on 2. Light stays off 3. Light flashes intermittently These observations will help determine if injectors are stuck open or malfunctioning.

Anonymous 2014-03-26 13:09

Fuel pressure: 40 psi with key off, and 50–60 psi with the key on. Additionally, the previous owner removed the check engine light bulb — possibly to hide a fault. The car ran perfectly for 112 miles before developing idle issues.

Anonymous 2014-03-26 13:10

When I manage to start it, the engine runs very roughly and stalls quickly.

Anonymous 2014-03-26 13:16

The security light is not on. This makes me skeptical of a security lock or ECU fault. However, the fact that the car starts with starting fluid suggests a fuel delivery issue. If injectors are staying open and flooding the engine, what could be causing this? I'm completely stumped.

Anonymous 2014-03-26 13:24

Please answer these key questions: 1. What is your fuel pressure? 2. How does the Noid light behave during cranking — steady on, off, or flashing? These answers will help evaluate whether injectors are stuck open. Note: If the Noid light stays on with no cranking, that indicates a serious issue. Additional caution: Check engine oil for signs of fuel contamination.

Anonymous 2014-03-26 13:45

With the key on and engine off, injectors should have 12V on the common wire (pink). The signal wire should NOT be grounded. If the signal wire is grounded, it will cause the injector to remain open and spray fuel continuously.

Anonymous 2014-03-27 13:52

I checked the oil — it appears thicker than normal and has a gasoline smell. Could this point to a crankshaft position sensor failure? If injectors are staying open, could a faulty crankshaft sensor cause this behavior? I performed the Noid test and observed no flashing — the light did not activate during cranking. What could be causing this?