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1997 Dodge Stratus 2.4L OBD2 Faults: P0134, P0112, and P1496 – Diagnosis & Sensor Data Issues

Model: 97 Stratus Fault Code: P0112 Posted: 2015-08-11 14:27

I'm troubleshooting a 1997 Dodge Stratus Base (2.4L automatic) with persistent OBD2 fault codes: P0134 (Oxygen Sensor B1 S1), P0112 (Intake Air Temperature Circuit Low Input), and P1496 (5-Volt Supply Voltage Low). I'm focusing on resolving the P1496 issue, which may stem from a shorted sensor, damaged harness, poor wiring connection, or a faulty ECM. I've tested both the MAT (Manifold Absolute Pressure) and IAT (Intake Air Temperature) sensor connectors independently: - The top two pins of the MAT connector show 5V and ground when unplugged. - One pin on the IAT connector reads 5V when ignition is on, regardless of whether the sensor is plugged in or not. I have not yet removed the IAT sensor due to difficulty accessing it. However, during a cold start, live data briefly showed an IAT reading of 260°F — consistent with expected values for a cold engine. During that same session, the upstream oxygen sensor read 4.9V, dropping slightly to 4.7V at 1800 RPM for a few seconds; downstream readings fluctuated but appeared normal. A key observation: when I attempt to view live sensor data via my OBD2 scanner (Windows 8.1, Easy OBDII v2.2.0), the software freezes and displays a blank screen — it waits indefinitely for sensor responses. This behavior occurs consistently after attempting to access real-time sensor values. After multiple engine restarts: - The Check Engine Light remains on, but no stored codes appear. - After several attempts (approximately 5–6), the fault codes reappear in the scanner. I’ve tested the scanner on my 1995 Tacoma and found it reliable there. To validate results, I’m now attempting to retrieve codes using the odometer display with the 'ignition key dance' method — a known workaround for some OBD2 systems. The P1496 code indicates sustained 5V supply below 4.4V — yet I measure exactly 5.0V at both MAT and IAT connectors when disconnected. This discrepancy raises concerns about the ECM or wiring integrity. Under the hood, near the fuse box, there are two computers: one on the right with top-mounted connectors, and one on the left with side connectors. Is either of these the Engine Control Module (ECM) or Powertrain Control Module (PCM)? I’ve also observed that several sensors appear to be powered via a common rail from PCM pin 43 — including ECT, IAT, oxygen sensors, and camshaft position. The MAP sensor shows consistent readings (12.9 psi at idle; drops to 1.5 psi when manually tested with vacuum). However, the vehicle emits smoke when warm, suggesting it may be running rich. Given that the car runs normally otherwise but exhibits erratic live data behavior and intermittent fault codes, I suspect a potential ECM issue — though I’m open to other explanations such as wiring faults or sensor malfunctions. I plan to perform direct resistance checks on oxygen sensor heater circuits and verify ground connections at pin 43 (common ground for multiple sensors). A crowfoot wrench is pending so I can remove the upstream O2 sensor for off-vehicle testing. Any insights into this behavior, especially regarding live data freezing or inconsistent readings, would be greatly appreciated.

Related fault codes

P0112P0134P1496

Comments (5)

Anonymous 2015-08-11 15:38

I'm going to take some time to go through your detailed post. Some initial thoughts: - P1496 could indicate a shorted sensor or wiring where the 5V signal is grounded. - A temporary troubleshooting step: test the Throttle Position Sensor (TPS). - If all other systems (AC, speedometer) are functioning normally, this may point to an ECM issue rather than a major electrical fault. - The software freezing when accessing live sensor data might be due to outdated or incompatible scanner software — try using a newer version that supports raw data streaming.

Anonymous 2015-08-15 21:11

Updated test results from today: - Using a different OBD2 software with raw data support, I observed the IAT sensor reading consistently at 260.6°F — even when unplugged or with engine off, as long as ignition is on. - When the two pins of the IAT connector are shorted together, the voltage drops to zero, but the temperature reading remains unchanged (still 260.6°F), suggesting a non-functional sensor signal path. Oxygen sensors: - Upstream O2 sensor reads 0.49V whether engine is running or off — and even when disconnected. It fluctuates slightly between 0.49V and 0.48V, likely due to sampling noise. - Downstream O2 sensor shows a stable 0.64V reading under the same conditions — unaffected by plug-in status. I attempted a propane test on the downstream O2 sensor but found it physically bent — likely dead. No response was observed even after heating. The upstream oxygen sensor remains inaccessible due to tight mounting; I’ll need a crowfoot wrench to remove it for off-vehicle resistance and heater testing. The MAP sensor appears functional: shows 12.9 psi at idle, drops to 1.5 psi when manually vacuumed (using a vacuum pump). This confirms it's working properly. Vehicle runs normally but emits smoke when warm — likely indicating a rich fuel condition. Given that the system relies only on intake vacuum and throttle position signals, this may suggest the vehicle is operating in limp mode or has an incorrect fuel trim calibration. Thanks for the detailed update.

Anonymous 2015-08-16 10:15

I haven’t yet tested the ECT (Engine Coolant Temperature) sensor. Based on schematics, it should have a tan wire with black stripe connected to PCM pin 26 (5V reference), and a black wire with light blue stripe — which is likely grounded at PCM pin 43. Could you confirm what voltage appears on the signal wire (tan wire) when the ECT sensor is unplugged? This would help verify if the ground or power circuit is intact.

Anonymous 2015-08-17 00:15

Thanks for your input. I haven’t yet tested the ECT sensor — the OBD scanner reading seems reasonable. According to online schematics, pin 61 of the PCM provides 5V power to both TPS and MAP sensors. Multiple sensors are connected via a common rail from PCM pin 43 (ground), including ECT, IAT, oxygen sensors, and the other side of the MAP sensor. This suggests that each sensor operates with an internal reference voltage — likely powered by a constant current source in the PCM — where resistance changes produce variable output voltages. I’ve only been able to access data from the second set of PCM connectors (pins 41–80). If my schematic is incorrect, I’m essentially working without full diagnostic visibility. I plan to perform direct wire resistance checks between O2 sensors and the PCM, as well as verify voltage on oxygen sensor heaters. The downstream heater fuse appears functional; all devices powered by the ASD relay are operating normally. I’ll use a crowfoot wrench soon to remove the upstream O2 sensor for off-vehicle heater resistance testing and a propane test to confirm functionality. Thanks again for your help.

Anonymous 2015-08-17 11:06

Check the oxygen sensors — a shorted harness could cause voltage to be grounded. Confirm that the O2 sensor heaters are powered (should be ON) and verify shared ground connections at pin 43 of the PCM. The ECT sensor is an easy point to probe for testing continuity or signal integrity.