My check engine light came on so I ran a diagnostic code came up as 1492 which shows it as ambient temperature sensor voltage too high

1991 is pre-OBD2. code readers will not work.
sorry.
however, all is not lost. Many cars have an alternate way of reading codes from the computer.
Toyota has a block under the hood and you short couple wires together and count engine light flashes
Chrysler you can turn the ignition key on and off a few times and count engine light flashes
in your case for GMs from 1982 to 1995
1: find the 12 pin connector under the dash and short the upper two rightmost terminals.
with the ignition "ON" and engine not running. The system will enter the diagnostic mode. In this mode, the computer will display a Code 12, three consecutive times, by flashing the "CHECK ENGINE", "SERVICE ENGINE SOON" or "MALFUNCTION INDICATOR LAMP" or light. A Code 12 consists of one flash, a short pause, then two flashes in rapid succession.
2:. After Code 12 is displayed, any stored trouble codes will be displayed by flashing the "CHECK ENGINE", "SERVICE ENGINE SOON" or "MALFUNCTION INDICATOR LAMP" light. All codes are displayed 3 times each then a code 12 will repeat. In the diagnostic mode, the computer will also energize all computer controlled relays and solenoids.

Tech -- GM 2 Digit codes for 82 and up (non OBD-II)
code - code definition
12- diagnostic mode
13- 02 sensor or circuit
14- coolant sensor or circuit/ high temp indicated
15- coolant sensor or circuit/ low temp indicated
16- system voltage out of range
19- crankshaft position sensor or circuit
21- throttle position sensor or circuit- voltage high
22- throttle position sensor or circuit- voltage low
23- mixture control (m/c) solenoid or circuit (carbureted models)
23- manifold air temperature (mat) sensor or circuit (1990 and earlier models)
23- intake air temperature (iat) sensor circuit (fuel-injected models)
24- vehicle speed sensor (vss) or circuit
25- manifold air temperature (mat) sensor or circuit - high temperature indicated (1990 and earlier models)
25- intake air temperature (iat) sensor or circuit - high temperature indicated (1991 and later models)
26- quad driver module circuit
27- quad driver module circuit
28- quad driver module circuit
29- quad driver module circuit
31- park/neutral position (pnp) switch circuit
32- baro sensor or circuit (carbureted models)
32- egr circuit (fuel-injected models)
33- manifold absolute pressure (map sensor signal voltage high
33- mass air flow (maf) sensor or circuit - excessive airflow indicated
34- manifold absolute pressure (map) sensor signal voltage low 34- mass air flow (maf) sensor signal - low airflow indicated
35- idle speed control (isc) switch or circuit (shorted) (carbureted models)
35- idle air control (iac) valve/ circuit
38- brake switch circuit
39- torque converter clutch (tcc) circuit
41- no distributor signals to ecm, or faulty ignition module ( carbed models)
41- cylinders select error- mem-cal or ecm problem ( fuel-injected models
41- cam sensor circuit (3.8 engine)
42- bypass or electronic spark timing (est) circuit
43- low voltage at ecm terminal l (carbureted models)
43- knock sensor circuit
44- oxygen sensor or circuit - lean exhaust detected
45- oxygen sensor or circuit - rich exhaust detected
46- power steering pressure switch circuit
48- misfire diagnosis
51- prom, mem-cal or ecm problem
52- calpak or ecm problem
53- egr fault (carbureted models only)
53- system over-voltage (ecm over 17.7 volts)
54- mixture control (m/c) solenoid or circuit (carbureted models)
54- fuel pump circuit (1986 and later models)
55- oxygen sensor circuit or ecm
55- fuel lean monitor (2.2l engine)
61- oxygen sensor signal faulty (possible contaminated sensor)
62- transaxle gear switch signal circuits
63- manifold absolute pressure (map) sensor voltage high (low vacuum detected)
64- manifold absolute pressure (map) sensor voltage low (high vacuum detected)
66- pressure sensor or circuit air conditioning

Well, I would say that it means that SOMEBODY is confused!

Diagnostic Test Code (DTC) P0072 is defined by SAE J2012 as "Ambient Air Temperature Sensor Circuit Low" DTC P0073 is defined as "Ambient Air Temperature Sensor Circuit High"

I do not know how the ambient air temperature sensor circuit could be faulted both HIGH and LOW at the same time.

The only thing I have ever seen cause something like this is when people try to install aftermarket "performance chips" on their vehicles which "lie" to the computer about what the ambient air temperature is.

Hi Cornejo:
The DTC (Diagnostic Trouble Code) P0700 code is not the actual code that is of concern. The P0700 code is stored in the engine computer.

This code means that there is a code stored in the Transmission computer. The trans computer sends a message to the engine computer that there is a trans code stored. This lets the engine computer turn on the "check engine" light.

You need to have the transmission computer scaned for codes to find out whats going on. Most code readers do not read trans codes, you need to have a scan tool that is able to do this.
This could mean almost any thing. Most trans codes are eletrical related with the allison transmission.
Here is the diagnosis chart for the P0700. Again, this code only means a trans code is set in the TCM, not a actual failure code.
--------------------------------------------------------------------------------------------------------
DTC P0700
Circuit Description
This diagnostic trouble code (DTC) indicates that a related transmission DTC set in the transmission control module (TCM). The engine control module (ECM) receives the TCM DTC information over the serial data circuit. The ECM turns ON the malfunction indicator lamp (MIL) when the TCM sends a message over the serial data circuit requesting MIL illumination.



Conditions for Clearing the DTC graphic
The control modul turns OFF the MIL after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A scan tool can clear the code from TCM history. The TCM automatically clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without failure.

1. Verify power and ground supplies to the TCM when the vehicle is cold.

2. If OK, depending on ambient temperature. If ambient temperature is high and the problem will not show, remove the TCM and place it in a freezer for a couple of hours.
3. If the ambient temperature is low remove the TCM to a warm area for a couple of hours.
4. After sufficiently cold or warm, install the TCM and drive the vehicle immediately.
5. If the ambient temperature is low and the transmission now shifts or the ambient temperature is high and the transmission will not shift replace the TCM.

Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day

it is "ambient/battery temp sensor too high" error. sensor is located i under your battery. you need to fix its connection and/or you will need a replacement.

P1492 AMBIENT/BATTERY TEMPERATURE SENSOR Voltage too high...

Maybe a broken timing belt? Engine still turning, but cam shaft stopped turning. Pistons hitting the open valves?

Mike Graham

The Check Engine light will light when the ECU stores a trouble code.
Counting the Flashes
To retrieve trouble codes, turn the ignition key to the "on" position with the engine OFF.
The Check engine light will flash many short blinks. The total number of blinks equals the code number. For example, flash,pause, flash,flash = code 12.If more than one code is stored, the Check engine light will flash the codes in sequence (lowest to highest) with a pause between each code. The codes will repeat until the key is turned to the OFF position.

11 Transaxle codes present 12 Diagnostic check only 13 Oxygen sensor circuit 14 Coolant sensor/high temperature 15 Coolant sensor/low temperature 17 PCM fault - pull-up resistor 19 6X signal fault (92-95 models) 21 Throttle position sensor-voltage high 22 Throttle position sensor-voltage low 23 IAT circuit low 24 VSS circuit-no signal 25 IAT circuit-Temp out of high range 26 Quad driver output fault 32 EGR system fault 33 MAP sensor - voltage out of range high 34 MAP sensor - voltage out of range low 35 IAC - rpm out of range 41 Ignition control circuit-open or shorted 42 Bypass circuit - shorted or open 41/42 IC control circuit grounded/bypass open 43 Knock sensor circuit shorted or open 44 O2 sensor indicates lean condition 45 O2 sensor indicates rich condition 46 Power steeringpressure circit(91 models)open or shorted 49 High idle indicates vacuum leak 51 PCM memory error 53 System voltage error 55 A/D error 58 trans fluid temperature too high 59 Trans fluid temperature too low 66/67 A/C pressure sensor 81 ABS message fault 82 PCM internal communication fault

Hello, It should actually be an oil sending unit, and is located on the back of the intake manifold to the left of the distributor. *The P0523 is Oil Pressure Sending Unit Voltage too high *P1693 Generic fault indicating a fault in the bus or PCM/ECM interface *P1682 - I can't find this code Anyways, I will post here all the error codes for future reference. Dodge Cummins Check Engine Error Codes Cycle Key on-off-on-off-on to read codes in odometer display P0002 ECM fuel calibration error P0016 Crankshaft/Camshaft Timing Misalignment/Out-of- Sync P0071 Ambient Temperature Sensor Performance / Rationality P0072 Ambient Temperature Sensor Low P0073 Ambient Temperature Sensor High P0088 Fuel Rail Pressure Too High P0106 Manifold Absolute Pressure Sensor Performance / Rationality P0107 Manifold Absolute Pressure Sensor Low P0108 Manifold Absolute Pressure Sensor High P0111 Intake Air / Charge Temperature Sensor Performance / Rationality P0112 Intake Air / Charge Temperature Sensor Low P0113 Intake Air / Charge Temperature Sensor High P0116 Engine Coolant Temperature Sensor Performance / Rationality P0117 Engine Coolant Temperature Sensor Low P0118 Engine Coolant Temperature Sensor High P0121 Accelerator Position Sensor (APPS) Signal Voltage Too Low P0122 Accelerator Position Sensor (APPS) LowAPPS Voltage Input Too Low P0123 Accelerator Position Sensor (APPS) Signal Voltage Too High P0128 Cooling System Error / Thermostat Rationality P0148 Fuel Delivery Error P0168 Fuel Temp Too High P0169 Water-in-Fuel Detected For Too Long P0192 Fuel Rail Pressure Sensor Low P0193 Fuel Rail Pressure Sensor High P0201 Fuel Injector 1 Circuit P0202 Fuel Injector 2 Circuit P0203 Fuel Injector 3 Circuit P0204 Fuel Injector 4 Circuit P0205 Fuel Injector 5 Circuit P0206 Fuel Injector 6 Circuit P0216 Fuel Injection pump Timing Malfunciton [new injector pump time] P0217 Coolant Temperature Too High P0219 Engine Overspeed P0230 Transfer pump circuit out of range P0234 Turbocharger Overboost Condition P0235 Turbocharger Boost Sensor A Circuit P0236 Turbocharger Boost Pressure Sensor Performance / Rationality P0237 Turbocharger Boost Pressure Sensor Low P0238 Turbocharger Boost Pressure Sensor High P0251 Fuel Injection Pump Mechanical Failure Fuel Valve Feedback Circuit P0252 Injection Pump Fuel Metering Control "A" Range/Performance P0253 Fuel Injection Pump Fuel Valve Open Circuit P0254 Fuel Injection Pump Fuel Valve Current Too High P0300 Multiple Cylinder Misfire P0301 Cylinder 1 Misfire P0302 Cylinder 2 Misfire P0303 Cylinder 3 Misfire P0304 Cylinder 4 Misfire P0305 Cylinder 5 Misfire P0306 Cylinder 6 Misfire P0335 Crankshaft Position Sensor Circuit P0336 Crankshaft Position Sensor Performance P0337 Crankshaft Position Sensor Circuit Low P0338 Crankshaft Position Sensor Circuit High P0340 Camshaft Position Sensor Circuit P0341 Camshaft Position Sensor Performance / Rationality P0370 Timing Reference High Resolution Signal "A" P0380 Intake Air Heater #1 Control circuit P0381 Wait-to-Start Lamp Inoperative P0382 Intake Air Heater #2 Control circuit P0460 Fuel Level Sensor A Circuit P0461 Fuel Level Sensor 1 Performance / Rationality P0462 Fuel Level Sensor 1 Low P0463 Fuel Level Sensor 1 High P0477 Exhaust Pressure Control Relay Low P0478 Exhaust Pressure Control Relay High P0480 Cooling Fan 1 Control Circuit/Open (Low Speed Fan Relay) P0483 Cooling Fan Speed P0500 Vehicle Speed Sensor 1 Circuit, or No Vehicle Speed Reference Signal 1 P0514 Battery Temperature Sensor Performance / Rationality P0516 Battery Temperature Sensor Low P0517 Battery Temperature Sensor High P0521 Oil Pressure Sensor Performance / Rationality P0522 Engine Oil Pressure Sensor/Switch Circuit Low Input P0523 Oil Pressure Sending Unit Voltage too high P0524 Oil Pressure Too Low P0532 A/C Pressure Sensor Low P0533 A/C Pressure Sensor High P0541 Intake Air Heater Relay 1 Low P0542 Intake Air Heater Relay 1 High P0562 Battery Voltage Low P0563 Battery Voltage High P0572 Brake Switch 1 Low P0573 Brake Switch 1 High P0576 Cruise Control Input Circuit Low P0580 Speed Control Multiplexed Switch 1 Low P0581 Speed Control Multiplexed Switch 1 High P0602 Control Module Programming Error/NotProgrammed P0604 Internal Control Module RAM Integrity Failure P0606 Internal ECM Processor P0607 ECU Internal Performance P0622 Generator Field Control Circuit P0628 Fuel Pump Relay Circuit Low, or Fuel Lift Pump Control Circuit Low P0629 Fuel Pump Relay Circuit High, or Fuel Lift Pump Control Circuit High P0630 VIN Not Programmed in PCM P0633 SKIM Key Not Programmed in PCM P0642 Sensor Reference Voltage 1 Circuit Low P0643 Sensor Reference Voltage 1 Circuit High P0646 A/C Clutch Relay Circuit Low P0647 A/C Clutch Relay Circuit High P0652 Sensor Reference Voltage 2 Circuit Low P0653 Sensor Reference Voltage 2 Circuit High P0698 Sensor Reference Voltage 3 Circuit Low P0699 Sensor Reference Voltage 3 Circuit High P0700 Transmission Control System (MIL Request) P0743 Torque Converter Clutch Circuit Electrical P0753 Shift Solenoid "A" Electrical P0837 Four Wheel Drive (4WD) Switch Performance / Rationality P0838 Four Wheel Drive (4WD) Switch Circuit Low P0839 Four Wheel Drive (4WD) Switch Circuit High P1488 Auxiliary 5 volt supply output is too low P1492 Ambient/batt temp sensor volts too high P1493 Ambient/batt temp sensor volts too low P1596 Speed Control Switch always high P1597 Speed Control Switch always low P1652 J1850 Communication Bus P1687 No Cluster BUS Message or No Messages from the Mechanical Instrument Cluster P1688 Internal Fuel Injection Pump Controller Failure P1689 No Communication Between ECM & Injection Pump Module P1690 Fuel injection pump CKP Sensor Does Not Agree With ECM CKP Sensor P1691 Fuel Injection Pump Controller Calibration Failure P1693 Generic fault indicating a fault in the bus or PCM/ECM interface P1757 Governor pressure is above 3 PSI when 0 PSI is requested P1762 Governor Press Sensor Offset Volts Too Low or Too High P1765 Transmission 12 volt supply relay control circuit P2121 Pedal Position Sensor 1 Performance / Rationality P2122 Pedal Position Sensor 1 Low P2123 Pedal Position Sensor 1 High P2127 Pedal Validation Switch 2 Low P2128 Pedal Validation Switch 2 High P2146 Fuel Injector Group 1 Supply Voltage Circuit P2149 Fuel Injector Group 2 Supply Voltage Circuit P2266 Water in Fuel Sensor Circuit Low P2269 Water in Fuel Condition P2502 Charging System Output Voltage P2503 Charging System Output Low P2504 Charging System Output High P2509 ECM/PCM Power Input Signal Intermittent P2607 Intake Air Heater Relay 2 Low P2608 Intake Air Heater Relay 2 High P2609 Intake Air Heater System Performance Hope this will help you. Cheers! Ryan

1491-radiator fan relay control circut
1492-ambient/battery temp sensor volts to high
check and make sure your radiator fan is coming on
samboiv